Heat recovery and demand ventilationsystem

ABSTRACT

A ventilation system for an air conditioning system includes dampers, a heat exchange unit, and a control unit. One damper controls the flow of ambient air into the system. The other damper controls the flow of relief/exhaust air that is cannibalized from return air from a room or space being cooled (or heated) by the air conditioning system. The ventilation system utilizes a control algorithm in the control unit to calculate, at stepped spaced apart increasing room ventilation rates, increasing CO2 concentrations in the air in the room that are below a maximum desired CO2 concentration in a room. The control algorithm permits a control unit in the ventilation system to open and close the dampers to maintain a CO2 concentration in the room that is below the desired CO2 concentration level.

This application is a continuation in part of U.S. patent applicationSer. No. 12/807,018 filed Aug. 26, 2010.

This invention relates to heating and air conditioning systems.

More particularly, the invention relates to a system to facilitateventilation air heat recovery and volume management while maintaining ahigh indoor air quality for human occupants. This invention willsubstantially reduce the energy consumption of heating and airconditioning systems in commercial and institutional buildings with highoccupant densities (greater than 20 people per 1,000 square feet ofoccupied space).

Commercial and institutional buildings have long been equipped withconstant air volume ventilation systems which employ a means for outsideair to enter and leave the building. Recent technology also employsventilation air volume control utilizing CO2 sensors and operabledampers. Such systems are controlled using a single point CO2 level asthe ventilation reference value and the objective is to preventobjectionable odors and vapors from accumulating in buildings.

It has for many years been desirable to provide, when possible,improvements to such ventilation air systems.

Therefore, it is a principal objective of this invention to provide animproved system to ventilate a building in the most cost effective,energy efficient manner, and meet the requirements of indoor air qualitystandards developed by recognized authorities in the industry,specifically, ASHRAE Standard 62.1-2010.

This and other further objects will be apparent to those skilled in theart from the following detailed description thereof, taken inconjunction with the drawings, in which:

FIG. 1 is a top view illustrating a retrofit module constructed inaccordance with one embodiment of the invention and installed in apre-existing air conditioning or heating system;

FIG. 2 is a top view further illustrating the retrofit module of FIG. 1;

FIG. 3 illustrates an IRV graph prepared in accordance with the systemof the invention;

FIG. 4 is a block flow diagram illustrating a heat transfer andventilation control system constructed in accordance with the invention;

FIG. 5 is a block flow diagram illustrating a logic sequence utilized bya controller in the system of the invention illustrated in FIG. 4;

FIG. 6 is a top view illustrating a retrofit module constructed inaccordance with another embodiment of the invention and installed in apre-existing air conditioning or heating system;

FIG. 7 is a top view further illustrating the retrofit module of FIG. 6and the mode of operation thereof;

FIG. 8A is a top view illustrating a duct-damper assembly in the moduleof FIG. 6 with the damper in a first operative position;

FIG. 8B is a top view illustrating the duct-damper assembly of FIG. 7with the damper in a second operative position;

FIG. 8C is a top view illustrating the duct-damper assembly of FIGS. 6and 7 with the damper in a third operative position;

FIG. 9 is a top view further illustrating portions of the duct-damperassembly of FIG. 8A;

FIG. 10 is a side view illustrating the drum damper scalloped arcsegment configuration;

FIG. 11 is a perspective view of the assembled duct-damper assembly ofFIG. 9 in conjunction with a control system and illustrating furtherconstruction details thereof;

FIG. 12 is a segregated perspective view of FIG. 11 illustrating anangled damper blade configuration and damper construction;

FIG. 13 is a segregated perspective view of FIG. 11 of the drum arcsegments illustrating the undulating surface extending between thescalloped edges of the damper;

FIG. 14 is a segregated perspective view of FIG. 11 of the solid drumtop and bottom of the damper assembly illustrating additionalconstruction and operational details thereof;

FIG. 15 is a segregated perspective view of FIG. 11 of the air diverterpanel illustrating additional construction and operational detailsthereof;

FIG. 16 is a top view illustrating a retrofit module constructed inaccordance with another embodiment of the invention and installed in apre-existing air conditioning or heating system;

FIG. 17 is a top view further illustrating the retrofit module of FIG.16 and the mode of operation thereof;

FIG. 18A is a top view illustrating a duct-damper assembly in the moduleof FIG. 16 with the damper in a third operative position;

FIG. 18B is a top view illustrating the duct-damper assembly of FIG. 18Awith the damper in a second operative position;

FIG. 18C is a top view illustrating the duct-damper assembly of FIG. 18Awith the damper in a first operative position;

FIG. 19 is a perspective view further illustrating portions of theduct-damper assembly of FIG. 18A;

FIG. 20 is a perspective view illustrating an alternate damperconstruction;

FIG. 21 is a front elevation view of the duct-damper assembly of FIG.18A in conjunction with a control system and illustrating furtherconstruction details thereof;

FIG. 22 is a side elevation view illustrating an alternate damperconstruction;

FIG. 23 is a front view of the damper of FIG. 19 illustrating theundulating surface extending between the scalloped edges of the damper;and,

FIG. 24 is a top view of the damper of FIG. 18A illustrating additionalconstruction and operational details thereof.

Briefly, in accordance with the invention provided are heat recovery andventilation improvements in combination with a building structure. Thebuilding structure includes a room with a minimum occupancy density of20 people per 1,000 square feet, an air conditioning system including aheat transfer coil, and a first section of duct D4 leading to the heattransfer coil of the air conditioning unit 22 to direct return air fromthe building structure over the coil. The building structure alsoincludes a second section of duct D2 leading away from the heat transfercoil to carry conditioned (heated or cooled) supply air S1 from the coilback into the building. The ventilation improvements in the buildingstructure comprise a retrofit heat recovery and ventilation control unit(DVHR) connected to the first section of duct D4. The DVHR unit includesa housing; a heat exchange unit 12; a section of duct D5 operativelyassociated with an outside ambient air source fan 13 to direct ambientair over the heat exchange unit 12 and into the first section of ductD1; an inlet damper 15 controlling the flow of ambient air into ductsection D5 and over the heat exchange unit into the first section ofduct D1; a section of duct D3 connected to the first section of duct todirect a portion R2 of the return air flowing through the first sectionof duct over the heat exchange unit and into the duct section D6directing the air to the outside atmosphere via exhaust/relief fan 14;an outlet damper 16 controlling the flow of the portion ofreturn/exhaust air R2 from the first section of duct D1 over the heatexchange unit and into the outside atmosphere; a control unit 30operatively associated with the inlet and outlet dampers to control therates of flow of ambient and exhaust/relief air, respectively, throughthe dampers; a first flow sensor 20B operatively associated with theinlet damper to generate signals to the control unit representing therate of flow of ambient air through the inlet damper 15; a second flowsensor 21 operatively associated with the outlet damper 16; and a CO2sensor in the room to generate signals to the control unit 30representing the concentration of CO2 in the air in the room. The DVHRalso includes a first fan 13 to direct ambient air into the section ofduct D5, over the heat exchanger 12, and into the first section of ductD1; a second fan 14 to direct return/exhaust air R2 through the firstsection of duct D1, through the heat exchanger 12, and through ductsection D6 and into the atmosphere. The ventilation control system alsoincludes an algorithm in the control unit 30 to calculate, at steppedspaced apart increasing room ventilation rates corresponding toincreases in room occupancy, acceptable CO2 concentrations below amaximum desired CO2 concentration in the room, and to increase ordecrease the outside air ventilation rate to achieve the acceptable CO2concentration.

In another embodiment of the invention, I provide improvements incombination with a building structure. The building structure includes aroom with a maximum occupancy rating of at least twenty individuals per1000 sq. ft. of occupied space, and an air conditioning system. The airconditioning system includes a heat transfer coil; a first section ofduct (D4) leading to the heat transfer coil to direct return air fromthe building structure over the coil; and, a second section of duct (D2)leading away from the heat transfer coil to carry air from the coil backinto the building. The improvements in the building structure comprise aretrofit ventilation control unit. The unit is attached to the firstsection of duct and includes a housing (23); a heat exchange unit (12);a third section of duct (D1) connected to the first section of duct (D4)to direct a first portion of return air from the room into the firstsection of duct; a fourth section of duct (D3) to direct a secondportion of return air from the room over the heat exchange unit; a fifthsection of duct (D5) to direct ambient air over the heat exchange unitinto the third section of duct (D1). The heat exchange unit maintainsthe second portion of return air separate from the ambient air andtransfers heat between the second portion of return air and the ambientair. The ventilation control unit also includes a sixth section of duct(D6) to direct the first portion of return air from the heat exchangeunit into the outside atmosphere; an outlet damper (16) controlling theflow of the second portion of return air over the heat exchange unit(12) and into the outside atmosphere; an inlet damper (15) controllingthe flow of the ambient air over the heat exchange unit (12); a controlunit operatively associated with the inlet and outlet dampers to controlthe rate of flow of the ambient air and the second portion of the returnair, respectively, through the dampers; a first flow sensor operativelyassociated with the inlet damper to generate signals to the control unitrepresenting the rate of flow of ambient air through the inlet damper; asecond flow sensor operatively associated with the outlet damper togenerate signals to the control unit representing the rate of flow ofthe ambient air through the outlet damper; and, a CO2 sensor in the roomto generate signals to the control unit representing the concentrationof CO2 in the air in the room. The improvements also include a first fanto direct the ambient air into the fifth section of duct, over the heatexchanger, and into the first section of duct; a second fan to directthe second portion of return air from the fourth section of duct, andthrough the fourth section of duct over the heat exchanger, and into theatmosphere; and, an algorithm in the control unit to calculate, atstepped spaced apart increasing room ventilation rates, increasing CO2concentrations in the air in the room that are below a maximum desiredCO2 concentration in the room.

In a further embodiment of the invention, improvements are provided Incombination with a building structure. The building structure includes aroom with a maximum occupancy rating of at least twenty people per 1,000sq. ft. of occupied space; and, an air conditioning system. The airconditioning system includes a heat transfer coil; a first section ofduct (D40) leading to the heat transfer coil to direct supply air fromthe building structure over the coil; and, a second section of duct(D20) leading away from the heat transfer coil to carry air from thecoil back into the building. The improvements in the building structurecomprise a ventilation control unit attached to the first section ofduct. The ventilation control unit includes a housing (230); a heatexchange unit (120); a third section of duct (D10) connected to thefirst section of duct (D40) to direct a first portion of return air fromthe room into the first section of duct; a fourth section of duct (D30)to direct a second portion of return air from the room over the heatexchange unit; a fifth section of duct (D50) to direct ambient air overthe heat exchange unit into the third section of duct (D10), the heatexchange unit maintaining the second portion of return air separate fromthe ambient air and transferring heat between the second portion ofreturn air and the ambient air, and to direct ambient air directly onlyto said third section of duct (D10) by bypassing the heat exchange unit;a sixth section of duct (D60) to direct the second portion of return airfrom the heat exchange unit into the outside atmosphere; an outletdamper assembly (160) controlling the flow of the second portion ofreturn air over the heat exchange unit (120) and into the outsideatmosphere; and, a generally semi-cylindrical inlet damper assemblycontrolling the flow of the ambient air into the ventilation controlunit. The inlet damper assembly including a member (38, 1150) rotatablebetween at least three operative positions, a first operative positiondirecting ambient air only over the heat exchange unit (120); a secondoperative position bypassing the heat exchange unit and directingambient air only directly to the third section of duct (D10) to combinewith the first portion of return air; and a third operative positionpreventing the ambient air from flowing to the heat exchange unit and tothe third section of duct (D10) to combine with the first portion ofreturn air. The ventilation control unit also includes a control unitoperatively associated with the inlet and outlet damper assemblies tocontrol the rate of flow of the ambient air and the second portion ofthe return air, respectively, through the damper assemblies; a firstflow sensor operatively associated with the inlet damper assembly togenerate signals to the control unit representing the rate of flow ofambient air through the inlet damper assembly; a second flow sensoroperatively associated with the outlet damper assembly to generatesignals to the control unit representing the rate of flow of a secondportion of return air through the outlet damper; and, a CO2 sensor inthe room to generate signals to the control unit representing theconcentration of CO2 in the air in the room. The improvements alsoinclude a first fan to direct the ambient air into the fifth section ofduct, over the heat exchanger, and into the first section of duct; asecond fan to direct the second portion of return air from the fourthsection of duct, and through the fourth section of duct over the heatexchanger, and into the atmosphere; and, a control algorithm in thecontrol unit to calculate, at stepped spaced apart regulated roomventilation rates, in response to increasing and reducing CO2concentrations in the air in the room that are above or below analgorithm calculated desired CO2 concentration in the room.

Turning now to the drawings, which depict the presently preferredembodiments of the invention for the purpose of illustrating the usethereof and not be way of limitation of the scope of the invention, andin which like reference characters refer to corresponding elementsthroughout the several views, in a preferred embodiment of theinvention, the EMS (Energy Management System) serves primarily as adiagnostic tool to provide graphic user interface (GUI) capability forthe entire campus HVAC and lighting systems. The GUI comprises acomputer screen with graph interface software and includes (1) on screenrepresentation of ambient air flow in cfm, (2) on screen representationof exhaust/relief air flow in cfm, (3) on screen representation of modeof operation i.e. (i) heat recovery heating mode (changeover function),(ii) heat recovery cooling mode (changeover function), and (iii)economizer cooling mode (changeover function), (4) on screenrepresentation of occupied ‘active’ or ‘inactive’ mode, (5) on screenrepresentation of which segment CO2 concentration limit is prevailing,(6) on screen representation of room CO2 concentration level, and (7)alarm functions associated with no air flow when dampers are expected tobe in some open position or registering air flow, open damper position,when no air is to be moving. Room ventilation control functions and allalgorithm defining characteristics, formulae and changeoverfunctionality are embedded in the programmable controller hardwarecontrol board and processor. Ventilation control functions include (1)determining if the DVHR is to operate in the heat recovery mode oreconomizer mode based on outside air temperature (changeover functions),(2) calculating the IRV based on the algorithm, (3) varying the outsideambient air damper to maintain the proper CO2 concentration limit, and(4) varying the exhaust/relief air damper position to maintain thecorrect volume of air based on the outside/ambient air quantity.Changeover functions include (1) heat recovery heating mode (changeoverfunction), (2) heat recovery cooling mode (changeover function), and (3)economizer cooling mode (changeover function). Input variables, i.e.room square footage, room ventilation rate (Va), people ventilation rate(Vp), (Occmax), are transmitted to the controller from external sources,i.e. plug-in interface tools, a keyboard or other data input means. Itis the intent of this embodiment of the invention to maintain a maximumsteady state ventilation to achieve less than the 700 ppm CO2 levelexposure limit defined in ASHRAE 62-200. The maximum steady stateventilation rate is the calculated IRV based on the two independentventilation rates of people and area. The steady state feature definesthat the 700 ppm concentration increase in CO2 above ambient isaccounted for in the algorithm in addition to the area ventilationrequirement. Further, the energy recovery principles employed in thisembodiment of the invention transfer a minimum of 60% of thedifferential dry bulb temperature energy from the high air streamtemperature to the lower air stream temperature.

During the summer (cooling) months, the higher outside air temperatureis transferred to the lower room relief air temperature. During thewinter (heating) months, the higher room relief air temperature willtransfer its heat to the lower outside air temperature. During periodsof time when free cooling is available, the heat recovery (temperaturetransfer) unit is by-passed. Heat recovery in the cooling mode should beactive at about 80° F. ambient temperatures and higher. Heat recovery inthe heating mode should be active at about 50° F. ambient temperaturesand lower. Economizer cooling should be the temperatures in between.These temperatures are usually ‘field’ adjustable so that when extremeconditions exist, the changeover temperatures can be reset withoutcompletely reprogramming the controller.

High occupant spaces historically experience transient and variableoccupant loads. Prior to the 2010 version of ASHRAE 62.1-2010, indoorair quality (IAQ) standards defined constant use ventilation rates whichinfluenced sizing of heating and cooling systems based on peak occupantloads. ASHRAE 62.1-2010 explains the intent of the ventilation standardswith respect to volatile organic compound (VOC) dilution ventilation andCO2/physiological odor management. Two ventilation rates areindependently derived to meet these separate IAQ comprising conditionsand the sum of the two rates are intended to define the stead state rateCO2+VOC dilution rates to achieve a maximum CO2 exposure of 700 ppmabove ambient.

The approach discussed below concerns the proper control of ventilation(ambient) air which is introduced into a room.

The Approach

ASHRAE 62.1-2010 requires a minimum cubic foot per minute (cfm) ofoutside air (Va) per square foot (sf) of occupied space (i.e., space ina room) for VOC dilution. Additionally, each person is assigned aventilation value (Vp) in cfm per person for CO2/odor management whichis based on occupant occupation or activity. All CO2 ventilation rateshave been developed with the intent that a change of CO2 concentrationin an occupied room will not be objectionable if the CO2 level is keptbelow 700 ppm above the outside ambient CO2 level. Since CO2 sensorsmeasure the total CO2 in air, ambient CO2 levels (OSACO2) need to bemeasured. Ambient CO2 levels normally are in the range of 300 to 500ppm. The maximum desired total CO2 concentration in a room in parts permillion (ppm) is then equal to (OSACO2+700), or 1000 to 1200 ppm. When aventilation system operates during periods when a room is occupied, andwhen a low occupant count is in the room, the CO2/odor managementdilution rate can be met with the minimum VOC ventilation rate. Theminimum ventilation rate equals (Va)(x), although this is a logicalexpression ASHRAE still requires separate dilution ventilation rates forCO2, even though it appears the VOC dilution rate can achieve bothcriteria.

If priority is placed on meeting the VOC ventilation requirementsindependently of the CO2 ventilation requirements, then upon start ofany initial space ventilation sequence, the VOC dilution ventilationrate will define any minimum ventilation rate requirement. If the VOCdilution air quantity remains an independent ventilation air quantity(variable) in the total required steady state ventilation ratecalculation, the resultant CO2 ppm concentration will always besubstantially lower than the maximum allowable 700 ppm exposure limit,even at full occupancy of the room.

-   1. The control logic for the ventilation set forth in the approach    discussed above requires an algorithm to define and respond to the    rate of change in the occupancy of a room. A minimum unreduced VOC    dilution ventilation air flow rate, (Va)(x) (where x=the sq. ft.    area of a room), remains a constant to the controller when the room    is occupied. ASHRAE 62.1-2010 defines a quantity of ambient    ventilation air, Vp, per person to insure that the CO2 concentration    in a room does not exceed a desired maximum concentration. Presuming    that the Vp is calculated to insure that the CO2 concentration in a    room does not exceed 700 ppm above the concentration, OSACO2, in the    ambient air, then the outside air flow increases in response to an    increase in occupant respiration (i.e., in response to an increase    in the number of occupants in a room or a change in their activity    level), and incremental target CO2 levels or checkpoints, RV, are    defined to simultaneously achieve a constant VOC dilution    ventilation rate and respond to increasing and decreasing occupancy    of a room. The controller ventilation algorithm described below uses    increases or decreases in room occupancy in incremental selected    segments, where n is the number of segments selected, IRV is the    size in cfm of each segment, and IRVpt is the estimated cumulative    number of persons in a reset segment and any preceding reset    segment. The number, and therefor the size, of each segment is    adjusted as desired. The design airflow of the VOC dilution    ventilation (i.e., the base ventilation rate of Rb=(Va)(x)) plus the    CO2 control ventilation (i.e., the size of each segment, IRV, times    the number of segments S_((1, 2, 3 . . . n))) is the divisor in the    algorithm. The dampers 15, 16 (FIG. 1) which regulate the amount of    outside air to the space have a defining minimum VOC dilution air    flow, (Va)(x), as the initial open position. The occupied mode is    determined by time schedule stored in the control unit 30 or by an    occupant sensing mechanism operatively associated with the control    unit 30. A velocity sensor utilizing a transducer records the inlet    air flow quantity and adjusts the damper position to maintain a    minimum set point. This is a pressure independent control function    which is employed for air quantity and quality management functions    of all air flow regulating devices in the system. When, as room    occupancy increases, a maximum cfm of incoming ambient ventilation    air, IRVcfm, is reached for a segment, the CO2 limit (i.e., the RV)    for that segment is the upper CO2 limit for the prior segment. The    minimum VOC ventilation rate=(Va)(x). This would suggest that the    CO2/odor management rate is a duplicate of the minimum VOC    ventilation rate. ASHRAE does not recognize this comparative    analysis.

The control unit 30 achieves this upper CO2 by adjusting the damper thatregulates the flow of incoming ambient air. In contrast, when theoccupancy levels in a room decreases and the CO2 concentration in theroom drops, the maximum cfm of a segment, IRVcfm, must be overshot by aselected amount before the target CO2 concentration is altered. Forexample, if in the system represented in FIG. 3, the room occupancy andCO2 concentration are decreasing, when the CO2 level reaches 668 ppm,coinciding with 228 cfm, the control unit 30 does not adjust the damperto achieve a CO2 concentration of 668 ppm (at 228 cfm) from 738 ppm(above 228 cfm) until the value drops to below the IRV cfm quantity of228 by at least 10% of the difference of the segment air quantity, whichin this case is 60 cfm×10%=6 cfm. This will allow the IRV to change oncethe outside air quantity reduces to less than 222 cfm. This percentageis a field adjustable value based on the normal occupancy of the spaceand how quickly it can gain or lose occupants. Its use is for thisexample.

When a building starts in the occupied ‘inactive’ mode, the ventilationrate is at its minimum. If no one enters the room, the room CO2concentration will be essentially the ambient CO2 level. It is theintent of the control function to move to the first calculated segmentRV upon occupant entry into the room. There is no way the ambient CO2level of the room can be maintained once people enter. Therefore, the RVadjustment takes place once the air quantity exceeds its segment limit.Using FIG. 3, RV2@550 ppm will be the first occupied ‘active’ value. At300 ppm (RV1), the ventilation rate is in the occupied ‘inactive’ mode.

The various necessary ventilation criteria set forth below areincorporated in the control unit 30 (FIG. 1). In one embodiment of theinvention, ASHRAE 62.1-2010 VOC and CO2 management air flow rates areprovided via a handheld plug-in. In another embodiment, this data isprogrammed into the control unit 30. When ASHRAE 62.1-2010 ventilationdata is revised, a plug-in or any other desired data entry system isutilized to update the control unit 30.

Prior art ventilation systems typically have either fixed or on/off flowrates. Outside air introduced into a room or other space must berelieved from the space. When a space has no operable windows or doorswhich communicate with outside (ambient) air, the intake and reliefsystems permit equal volumes of air in and air out. Gravity air reliefsystems are most common. Exterior relief hoods or louvers are connectedto a building or space via either a direct duct and grille in theceiling, or a return/relief air grill in the ceiling which communicateswith a return/relief air plenum.

During any ambient climate temperature condition, when the outside aircan provide a lower temperature source to the air conditioning systemthan the set point of the temperature sensor without over cooling thespace, the outside air supply source should not be tempered to a highertemperature in the heat exchange unit 12 (FIG. 1). This defeats thecooling process. Instead, in one embodiment of the invention, in thefree cooling mode outside air is introduced to the return air path inthe manner indicated by arrow A2 in FIG. 2, bypassing the heat exchangeunit 12. This lowers the return air temperature to the air conditioningunit 22, thereby reducing the amount of compressorized cooling energyrequired to maintain the set point temperature in a room or other space.This is called the partial outside air economizer mode. Excess airgenerated by introducing air in a room or other space during the partialoutside air economizer mode is relieved from the space via a gravityrelief air system. The gravity relief air system has a back draftregulating damper to prevent outside air from entering into the buildingwhen the air conditioner if off. The back draft damper can be fittedwith either a counterbalanced barometric relief damper or anelectronically operated motorized damper. Either kind of damper willopen when the air conditioner is operating during the partial outsideair economizer mode.

When the ambient climate temperature conditions are not suitable foreither free cooling or reduced compressorized cooling, the gravityrelief air system is disabled and the heat exchange unit 12 is enabled.The heat exchange unit 12 works efficiently down to about 20% of themaximum air flow rate. In the system illustrated in FIG. 3, the maximumair flow rate is 408 cfm.

In the heat recovery mode of the module 10 (FIGS. 1 and 2) of theinvention, as the ventilation air quality increases and decreases,dampers 15 and 16 are operated by the control unit 30. The control unit30 ordinarily comprises a microprocessor. The control unit 30 utilizesthe ventilation algorithm described below, along with any other desiredalgorithms. Ambient air that is introduced through damper 15 asventilation air is compensated for by exhaust/relief air R2 (FIG. 1)that is directed over heat exchanger 12 and into the ambient atmospherevia damper 16. A minimum desired flow rate for ambient air throughdamper 15 is determined by the potential for trapping air borneparticulates in the heat exchange unit 12 when the air velocity drops tobelow the manufacturer recommend air flow. Some manufacturers permit anair flow rate that is less than 20% of the maximum desired air flow rateover heat exchanger 12. In FIG. 3, the maximum desired air flow rate ofventilation air is 408 cfm.

Where occupied spaces communicate with the outside ambient air viaoperable windows and doors, a minor positive air pressure is maintainedto minimize migration of air borne particulates into a room or otherspace. Such minor positive air pressures are not set forth in publishedstandards, but up to 20% of the design maximum air flow rate (408 cfm inFIG. 3) can be diverted to the pressurization mode with minimal energyrecovery impact at the design maximum desired air flow rate (i.e., airflow at peak occupancy). In FIG. 3, the maximum air flow rate is 408cfm. It is recommended that no more than 10% of the maximum air flowrate (i.e., in the system of FIG. 3 this would be 40.8 cfm) be relievedfor ventilation air flow up to 50% of the maximum air flow rate, andthat the 20% maximum pressurization air flow quantity should not beexacted on the system until 80% of the design maximum desired air flowrate is in use.

The heat recovery operation mode requires verifiable air flowmeasurements for proper application of the ventilation algorithm. Inorder to maximize the reduction in energy required to operate thesystem, the flow rates of the incoming ambient ventilation air and ofthe exhaust/relief air stream should be the same or nearly the same.Toward this end, each air inlet (or outlet) is provided with a velocitysensor 20A, 20B, 21. It may be possible to use a common sensor fordampers 15 and 17 because these dampers will not open together. Eachsensor is preferably calibrated and can operate to within 2% accuracy atvelocity pressures as low as 250 fpm (0.03″ velocity pressure) at sealevel.

During low occupant loads in a room or other building space, only aminimal amount of exhaust air, R2, may be available for heat recovery.During such periods of low ventilation air flow, however, the outsideair cooling load on the room air conditioning system is also low,resulting in a minor increase to the cooling load of the airconditioning equipment above minimum (no outside cooling load).Algorithm calculated indoor air quality (IAQ) conditions arecontinuously maintained regardless of the quantity of exhaust air, R2,utilized.

The combination of heat recovery and demand ventilation control enablesa substantial reduction in energy use, enables increased sustained IAQ,and enables enhancements in sustainable system performance. Enhancementsinclude:

-   -   a. Reduction of AC unit sizes based on the reduction of the        cooling load    -   b. Reduction of electrical service size based on smaller        electrical loads of the smaller AC units    -   c. Energy reduction of HVAC system energy use of 25%-40%    -   d. Improvements of indoor air quality (IAQ)]        -   i. Stable CO2 levels        -   ii. Adequate VOC dilution        -   iii. Reduction of space temperature variations        -   iv. Noise reduction    -   e. Reduction of the carbon footprint with the reduction of        required utility generation    -   f. Air conditioning system benefits        -   i. Reduction of entering air temperatures to the evaporator            and the resultant high differential pressures at the            compressor        -   ii. LEED compliance for all refrigerant systems if the            normal size refrigerant charge is compared with the reduced            unit size charge        -   iii. Minimizing excess outside air into the building when            occupancy is not at maximum        -   iv. Partial outside air economizer use (not available with            conventional heat recovery modules)        -   v. Operable in all ambient temperatures from −10° F. to 120°            F.    -   g. Hydrocarbon power generator emitted pollution reduction at        generating plants    -   h. Water use reduction for cooling of utility generator        equipment    -   i. Reduction of global warming    -   j. Refrigerant volume leakage reduction in package air        conditioning equipment    -   k. Reduction of water chemical treatment at industrial cooling        towers of utility generating plants    -   l. Reduction of ozone depleting and global warming refrigerant        leakage.

Use of an occupant sensor(s) to manage IAQ and energy consumption iscomplimentary to a lighting control system. A lighting control system isan energy management tool required by the International EnergyConservation Code as an alternative to time clocks which use spaceoccupant overrides for the light control system. One presently preferredoccupant sensor utilizes infrared temperature sensor technology todetermine the number of occupants in a room. Any human entry in to thesensor zone is detected and turns on light fixtures. EMS systems cancontrol space lighting and HVAC during present hours of operation.Substantial energy and cost savings are realized if the sensor determinethe presence of occupants and turn energy consuming systems on or off.Such an occupancy sensor can be furnished with an auxiliary contact toenable independent functioning of the lighting system from the HVACsystem. The auxiliary contact determines if a ventilation adjustment isin order. The occupancy sensor also enables the “occupied” modetemperature sensor set point to be changed in response to an “active”status versus an “inactive” status. If, for example, during a scheduled“occupied” mode of the HVAC unit, the room sensor detects no humanpresence for a selected time period of five minutes, the HVAC unitserving the room can change to “occupied-inactive” status. This changesthe room people and ventilation set points to zero outside air. When theroom sensor detects human presence, the operating sequence for the DVHR(Demand Ventilation Heat Recovery) unit 10 of the invention begins. Thefirst stage of the ventilation air management mode is utilized when aroom is not occupied and is based on the outside ambient air temperatureand includes the base ventilation rate, Rb=(Va)(x). Since the room isnot occupied, (Vp)(Occact)=0. An outside air source temperature sensordetermines if unit 10 operates in the Cooling-Heat Recovery (CHR) mode,the Heating-Heat Recovery (HHR) mode, or the Economizer-No Heat Recovery(EHNR) mode. When unit 10 operates either of the CHR or HHR modes, theoccupancy sensor enables the “occupied-active” mode of the HVAC system.The ventilation ambient air damper 15 and the exhaust air damper 16(FIG. 1) are opened, closed, or not adjusted in order to direct into theroom the minimum necessary quantities of ventilation air as calculatedby the ventilation algorithm. The velocity sensors 20A, 20B, 21, theindoor and outdoor temperature sensors, and the CO2 sensor in the roomprovide inputs to the EMS (Energy Management System). The indoor airquality (IAQ) and indoor and outdoor temperature sensors enable thecooling and heating systems to operate and the ventilation systemalgorithm determines calculates the RV set point of the room.

When operating in the ENHR mode, the bypass damper 17 (FIG. 2) is openedto its design maximum air flow as sensed by the velocity sensor 20A. Themaximum outside air volume is calculated by the engineer using the peakair flow of the supply fan 13 divided by the number of DVHR units on itssystem. During the ENHR mode, the heat recovery module air pressure dropis excluded from the system losses because it is bypassed. This allowsfor the supply fan 13 to ramp up to a higher air flow because it doesn'thave as much system resistance to overcome. This is a higher airquantity than the maximum fan capability if the sum of the totalventilation air flow required for proper IAQ is tabulated. This is ascheduled value on the drawings usually defined by the engineer.

The exhaust/relief damper 16 and the heat exchanger damper 15 areclosed. Air is relieved from the room via a gravity relief system. Whenthe ambient air quantity produces a temperature which is too cold andthe room temperature drops to below the desired set point, the quantityof ventilation air is controlled based on readings produced by the roomCO2 sensor until the IAQ set point can not be met and the temperatureset point continues to drop. When this occurs, the HHR mode is enabled.In most cases, the morning warm-up condition shall enable the HHR mode.After the system begins operating in the HHR mode, the ENHR mode isenabled once the outside air temperature reaches 60 degrees F. orreaches another selected temperature. If at any time the ambient airtemperature exceeds the set point of the room by five degrees F., theCHR mode is enabled.

An infrared sensor in the room or other space determines when the roomis occupied. When the room is not occupied, the ventilation system ofthe invention is in an ‘inactive’ mode. When the room is occupied, thesensor generates and transmits signals to control unit 30. Control unit30 places the ventilation system in the active mode, which triggers useof EQ. 1 (and consequently a graph comparable to that of FIG. 3) as setforth below.

Control unit 30 communicates with fans 13 and 14 to turn the fans on andoff and to adjust the speed of operation of the fans.

The ventilation unit 10 illustrated in FIGS. 1 and 2 includes a housing23, heat exchange unit 12 mounted in housing 23, damper(s) 15, 16, and17 mounted in housing 23, velocity sensors 20A, 20B, and 21 mounted inhousing 23, and a controller 30 mounted in the housing 23. Fans 13 and14 can be mounted on housing 23, or can be mounted at locations separatefrom housing 23 to direct air through ducts that are connected tohousing 23.

Duct D5 guides incoming ambient ventilation air A1 over one side of heatexchange unit 12, out into the duct of D1, and through duct D4interconnecting unit 10 and air conditioning unit 22 (FIG. 2). Duct D3guides a portion R2 of the return air over the other side of heatexchange unit 12 and out into the ambient air as exhaust/relief air. Thereturn air comes from the room being ventilated by unit 10. Dampers 15and 17 are mounted in duct D5. Damper 16 is mounted in duct D6.

Velocity sensors 20A, 20B, 21 are shown mounted in ducts D5 and D6, butthat need not be the case. Sensors can be mounted at any desiredlocation in ventilation unit 10 to obtain an accurate reading ofventilation air A1 entering duct D5 and of return air R2 exiting duct D6as exhaust/relief air.

Velocity sensors 20A, 20B, 21 are operatively associated with controlunit 30 and generate and transmit signals to control unit 30 definingthe velocity of ambient air, indicated by arrow A1, traveling throughducts D5 and D1 into duct D4, and of return air, indicated by arrow R2,traveling through ducts D1 and D6.

Control unit 30 also receives signals from a CO2 sensor (not shown) inthe room or other space being cooled (or heated) by the air conditioningunit 22. Control unit 30 can also, if desired, receive signals from asensor that detects ambient temperature, from a sensor that detects thetemperature in the room being cooled (or heated) by unit 22, from aninfrared or other sensor that detects when one or more individuals arein the room, and from a sensor that indicates the desired temperatureset point in the room.

While the shape and dimension of ventilation unit 10 can vary asdesired, and unit 10 can be installed at any desired location near to orspaced apart from air conditioning unit 22, the embodiment of theinvention illustrated in FIGS. 1 and 2 is a preferred embodiment becauseit is constructed to be inserted after a portion of ducting that leadsto and carries return air to a previously installed air conditioningunit 22 is removed. After the portion of the return air ducting leadingto the air conditioning unit 22 is removed, unit 10 is installed in-lineto replace the portion of the return air ducting that was removed.Accordingly, return air R1 and R2 from the room flows into unit 10,portion R1 flows into ducts D3, D1 and D4 and into air conditioner 22,and portion R2 flows over or through heat exchanger 12 and out throughduct D6. This, as can be seen in FIG. 2, eliminates or minimizes theamount of duct which must be utilized to install unit 10 in-line along areturn air duct that is connected to air conditioner 22. In FIGS. 1 and2, it is assumed that unit 10 is located outdoors. Unit 10 can also, ifdesired, be installed in a duct which is located indoors, or can beinstalled at any other desired location. And, as would be appreciated bythose of skill in the art, unit 10 can be utilized and installed when anew air conditioner is being installed on or adjacent a buildingstructure, or can be installed as an integral part of air conditioningunit during the manufacture of a new or refurbished air conditioningunit. Unit 10 is preferably, but not necessarily, manufactured as aself-contained module with a control unit 30 designed to receivenecessary inputs from air velocity sensors 20A, 20B, 21, from a room CO2sensor, from a room infrared occupancy sensor, from an ambient airtemperature sensor, or from any other desired sensor that is part ofself-contained unit or that is remote from unit 10. Fans 13 and 14 canbe incorporated as a part of unit 10, or can be omitted from unit 10 andinstalled in or adjacent ducting that leads to unit 10. Similarly,dampers 15 to 17 can, as illustrated in FIGS. 1 and 2, be incorporatedas part of unit 10, or can be omitted from unit 10 and installed inducting leading to unit 10, as can control unit 30, velocity sensors20A, 20B, 21, and heat exchange unit 12. The compact moduleconfiguration, with or without fans 13 and 14, illustrated in FIGS. 1and 2 is presently much preferred in the practice of the invention.

As is illustrated in FIG. 1, a portion, R2, of the return air from theroom is directed by fan 14 from duct D1 over one side of heat exchangeunit 12 and into the ambient air as exhaust/relief air. The size, incfm, of portion R2 is controlled by damper 16. Another portion R1 of thereturn air from the room continues through ducts D1 and D4 to airconditioning unit 22, where it travels over the cooling (or heating)coils and becomes part of the supply air, indicated by arrow S1,traveling through duct D2 to the room.

As is also illustrated in FIG. 1, ambient air, indicated by arrow A1, isdirected by fan 13 over the other side of heat exchange unit 12 and intoduct D1. This ambient air travels over the cooling (or heating) coils inair conditioning unit 22 and becomes part of the supply air, indicatedby arrow S2, to the room.

When the ambient air is warmer than the desired temperature of the room,heat exchange unit 12 functions to transmit heat from the ambient air A1to return air R2. When the ambient air A1 is cooler than the desiredtemperature of the room, heat exchange unit 12 functions to transmitheat from the return air R2 to the ambient air, A1.

In FIG. 2, damper 15 is closed. Ambient air A2 entering duct D5 travelsthrough damper 17, through ducts D1 and D4, and into air conditioningunit 22. The operational configuration of FIG. 2 is utilized when theambient air temperature is sufficiently cool to provide desired coolingto return air R1.

In FIGS. 1 and 2, D1 is an air duct integrated with D3 for return air toair conditioner 22; D2 is an air duct directing cooled (or heated)supply air S1 from air conditioner 22 back to the room; D3 is a ductthrough which return air from the room flows in unit 10; D4 is a ductthat directs return air into the coil/fan section of air conditioner 22;D5 is a duct that directs ambient air A1 into unit 10 and over one sideof heat exchange unit 12; D6 is a duct that directs exhaust/relief airfrom heat exchanger 12 into the ambient atmosphere; A1 and A2 areambient air streams flowing into duct D5; A1 is a fan induced ambientair stream directed through or over heat exchange unit 12; A2 is a faninduced ambient air stream that bypasses heat exchange unit 12 andtravels directing in the return air stream in the manner illustrated inFIG. 2; R2 is a portion of the return air stream that is drawn over orthrough heat exchange unit 12; and S1 is a combination of return air R1and outside ambient air A1. FIG. 1 illustrates the heat recovery mode ofthe ventilation system of the invention. FIG. 2 illustrates theeconomizer mode of the invention. In the economizer mode, thetemperature of the ambient air stream A2 permits it to be added directlyto the return air stream R1 and obviates the necessity of passing anambient air stream A1 over or through heat exchanger 12.

A control system ventilation formula is used to calculate the CO2 ppmtarget concentration levels that are required to maintain in a room amaximum 700 ppm CO2 exposure level for occupants as defined in ASHRAE62.1-2010 (and earlier versions). This maximum 700 ppm CO2 exposure isin addition to the existing CO2 concentration in the ambient air.

There are two additive variables required to meet the ASHRAE standards:

a. One variable is the base “area ventilation rate”, i.e., theventilation rate required for a room.b. The other variable is the “person” ventilation rate, i.e., theventilation rate to compensate for each person in a room.

The calculation used below approaches each of the additive variables toachieve a critical steady state result based on maintaining a maximumCO2 concentration of 700 ppm above the CO2 concentration in the ambientair.

Variables Used in Conjunction with the Control System VentilationFormula

-   x=square footage of the room-   Va=area (i.e., room) ventilation rate requirement in cubic feet per    minute (cfm/sq. ft), as listed in ASHRAE 62.1-2010, Table 6.1.-   Occmax=maximum code or user defined number of occupants in room-   Vp=“per person” ventilation rate requirement, in cfm/person, as    listed in ASHRAE 62.1-2010 Table 6.1.-   CRT=rate reset variable based on outside air temperature during the    cooling mode. This is used in relation to Va.    -   CRT=1.0 for ambient less than or equal to 95 F    -   CRT=0.8 for ambient less than or equal to 96 F and greater than        95.    -   CRT=0.6 for ambient temperature less than or equal to 97 F and        greater than 96 F.    -   CRT=0.4 for ambient temperature less than or equal to 98 F and        greater than 97 F.    -   CRT=0.2 for ambient temperature less than or equal to 99 F and        greater than 98 F.    -   CRT=0.0 for ambient temperature greater than 99 F.    -   In other words, if the ambient temperature is greater than 99 F,        ambient air is not utilized to meet the area ventilation rate        requirement, but is still used to meet the “per person”        ventilation requirement.    -   The CRT values are adjustable with a plug-in to take into        account sensible cooling excesses associated with extremely high        ambient conditions.    -   Similar adjustments can be defined for very humid locations and        will be based on a relative humidity—dry bulb temperature        measurement which equals a wet-bulb temperature on the        psychometric chart.-   HRT=rate reset variable based on outside air temperature during the    heating mode. This is used in relation to Va.    -   HRT=1.0 for ambient temperature greater than 25 F.    -   HRT=0.8 for ambient less than or equal to 25 F and greater than        24.    -   HRT=0.6 for ambient temperature less than or equal to 24 F and        greater than 23 F.    -   HRT=0.4 for ambient temperature less than or equal to 23 F and        greater than 22 F.    -   HRT=0.2 for ambient temperature less than or equal to 22 F and        greater than 21 F.    -   HRT=0.0 for ambient temperature less than or equal to 21 F.    -   HRT values are adjustable using a plug-in to take into account        sensible heating excesses associated with extremely low ambient        conditions.-   OSACO2=concentration of CO2 in ambient air in ppm.-   Occact=count of number of people in room, usually determined by a    CO2 concentration that is in excess of the CO2 concentration in the    ambient air.-   IRV graph=a plot of selected spaced apart reset values (RVs). The    units of measure on the vertical axis of the graph are ppm (parts    per million) CO2. The units of measure on the horizontal axis of the    graph are cfm (cubic feet per minute) ventilation air.-   Rb=base ventilation rate for a room in cfm=(Va)(x).-   n=the number of cfm reset segments selected for and represented on    an IRV graph. Each cfm reset segment s ordinarily of equivalent size    to other segments, although this is not necessarily the case. IRV is    the size of each segment in cfm.-   IRVpt=the cumulative number of calculated persons in a reset segment    and any preceding reset segments.-   IRVcfm=a selected cfm point on the horizontal axis of an IRV graph    at which a reset segment ends, at which an associated reset value    (RV) occurs, and which represents a cumulative quantity (in cfm) of    outside (ventilation) air that is utilized. The value of such a cfm    point is equal to:

(Vp)(IRVpt)+(Va)(x)

-   IRV=the size in cfm of each segment in an IRL graph. IRV equals the    maximum outside air quantity (Vp×Occmax) divided by the number of    reset segments (n) selected. If, for example, five reset segments    are selected, the reset values (RV), or check points, occur at 0%,    20%, 40%, 60%, 80%, and 100% of the maximum (Vp×Occmax) outside air    ventilation (in cfm) that will be utilized to offset the    concentration of CO2 in the room that is above the concentration of    CO2 in the ambient air. Each segment extends from one RV to an    adjacent RV. For example, one segment extends from the cfm    associated with the RV at 0% to the cfm associated with the RV at    20%. If ten reset segments are selected, the reset values occur at    0%, 10%, 20%, 30%, 40%, etc. of the maximum flow of ambient air that    will be utilized to ventilate the room to offset CO2 concentrations    above the CO2 concentration in the ambient air.-   RV=RVd+OSACO2=a reset value on an IRV graph. The number of RVs    presently is one greater than the number, n, of segments. Each set    value (RV) represents a desired CO2 concentration which is noted on    the vertical axis of the graph and which is associated with a    selected cfm point (IRVcfm) on the horizontal axis of the graph. The    value of the selected cfm point (IRVcfm) indirectly indicates the    “metabolic equivalent” number of people (Occact) in the room, i.e.,    the value of the selected cfm points less the base cfm of (Va)(x) is    divided by Vp to give the “metabolic equivalent” number of people in    the room. A reset value (RV) defines a desired total room CO2    concentration limit at its associated IRVcfm. A velocity sensor 20A,    20B in the incoming supply stream of ambient air indicates the cfm    of the incoming air stream. As reset value (RV) is used to reset the    CO2 maximum allowable ppm value for its associated IRVcfm. The    control system of the invention sends a signal to the outside or    ambient air stream damper motors which modulate the damper blades to    adjust the outside air quantity in response to the CO2 concentration    detected by CO2 sensor(s) and in response to how much the room CO2    deviates from the CO2 concentration defined by the RV.-   RVd=the difference, in ppm, at a selected cfm point on an IRV graph    (IRVcfm) between the RV at that cfm and the ambient air CO2    concentration (OSACO2). Also known as CO2max.-   S_((0, 1, 2, 3, . . . n))=a numerical value (0, 1, 2, 3 . . . n)    representing the number of segments used in calculating, with the    formula noted below, both an RV and the amount by which the RV    exceeds the ambient CO2 concentration. For example, when the first    set point RV1 is calculated, a numerical value of 0 is used for S;    when the second set point RV2 is calculated, a numerical value of 1    is used for S; when the third set point RV3 is calculated, a    numerical value of 2 is utilized, and so on. When S=0, a segment is    not utilized and the RV=OSACO2.-   Altcorr=an altitude correction value. This value increases the IRV    values above those established for sea level and extends the    applicable segment maximum CO2 ppm value to a higher cfm value. This    is a multiplier to the IRV segment values. The value is based on the    specific density of air at sea level divided by the specific density    of air at the altitude of the project site. When the location of a    project is at sea level, the Altcorr is 1.0.-   CO2max=the desired maximum CO2 concentration in ppm in a room above    the CO2 concentration in the ambient air.-   CO2target=RVd=the target CO2 (above ambient) for a segment.-   Vamb=the cfm of ambient ventilation air entering the system as    measured by a velocity sensor.-   Vexit=the cfm of supply air that exits into the atmosphere after    passing by the heat exchanger as measured by a velocity sensor.-   CO2act=the actual measured CO2 in a room as measured by a CO2    sensor.-   Tact=the actual temperature in a room as measured by a thermostat.

Control System Ventilation Formula

Given the above variables, the target CO2 above ambient, or RVd, for asegment is:

$\begin{matrix}{{RVd} = {\frac{\begin{bmatrix}{{\left( {{CRT}\mspace{14mu} {or}\mspace{14mu} {HRT}} \right)({Rb})\left( {{OSACO}\; 2} \right)} +} \\{({Occact})({Vp})\left( {{{OSACO}\; 2} + {{CO}\; 2\max}} \right)}\end{bmatrix}}{({Rb}) + {{{IRV}({Altcorr})}\left( S_{({0,1,2,{3\mspace{14mu} \ldots \mspace{14mu} n}})} \right)}} - {{OSACO}\; 2}}} & \left\lbrack {{EQ}.\mspace{14mu} 1} \right\rbrack\end{matrix}$

The following example is presented by way of illustration, and notlimitation, of the invention.

Example

In this example, it is assumed that a room will be occupied by schoolchildren in the age range of 5 to 8. The ambient temperature is 88degrees F. The room is located as sea level. The size of the room is 900square feet. The CO2 concentration in ambient air is 300 ppm. Fivesegments are selected to use in preparing an IRV graph. The followingvalues are utilized:

-   n=5-   No. of RV points on IRV graph=n+1=6-   No. of occupants in a segment=(Occmax)/n=30/5=6-   x=900 sq. ft. (size of room)-   Va=0.12 cfm/sq. ft (from ASHRAE 62.1-2010: Table 6.1: Minimum    Ventilation Rates In Breathing Zone).-   Rb=(Va)(x)=(900)(0.12)=108 cfm-   Occmax=30 (maximum number of children allowed in room per building    code)-   Vp=10 cfm/person (from ASHRAE Table 6.1).-   CRT=1.0 (ambient temperature is less than 95 F)-   HRT=N/A, because the ambient temperature requires cooling, and not    heating.-   OSACO2=300 ppm.-   IRV=(Vp)(Occmax)/n=(10)(30)/5=60 cfm-   Occact=number of people in the room. This number times (Vp) is added    to Rb to determine the maximum airflow in a segment on an IRV graph.    The first segment includes 6 occupants. Six occupants times    (Vp)=6×10 cfm=60 cfm. 60+108=a maximum airflow of 168 cfm at the    upper end of the first segment in the IRL graph. The second segment    would also include 6 occupants, producing a total room occupancy    equal to the occupancy in the first segment plus the occupancy in    the segment or 6+6=12. Twelve occupants times (Vp)=12×10=120 cfm.    120+108=a maximum airflow of 228 cfm at the upper end of the second    segment in the IRL graph, and so on.-   Altcorr=1.0. The project site is at sea level.-   CO2max=700 ppm. This value is a constant for all building types and    occupancies.-   S_((0, 1, 2, 3 . . . n))=S_((0, 1, 2, 3, 4, 5))    Since CRT and Altcorr are each equal to 1.0, the control system    formula is simplified to:

$\begin{matrix}\begin{matrix}{{RVd} = {\frac{\begin{bmatrix}{{({Rb})\left( {{OSACO}\; 2} \right)} +} \\{({Occact})({Vp})\left( {{{OSACO}\; 2} + {{CO}\; 2\max}} \right)}\end{bmatrix}}{({Rb}) + {{IRV}\left( S_{({0,,1,2,3,4,5})} \right)}} - {{OSACO}\; 2}}} \\{= {\frac{\left\lbrack {32\text{,}400} \right) + {({Occact})\left( {10\text{,}000} \right)}}{(108) + {(60)\left( S_{({0,1,2,3,4,5})} \right)}} - 300}}\end{matrix} & \left\lbrack {{EQ}.\mspace{14mu} 2} \right\rbrack\end{matrix}$

At the first set point of 0%, Occact=0 (0% of the maximum occupancy of30 students=room is not occupied), S_((0, 1, 2, 3, 4, 5))=0, and theformula is

$\begin{matrix}{{{\left( {{Unoccupied}\mspace{14mu} {condition}} \right){RVd}\; 1} = {{\frac{32\text{,}400}{108 + {(60)(0)}} - 300} = {0\mspace{14mu} {ppm}}}}\mspace{20mu} {{{RV}\; 1} = {300\mspace{14mu} {{ppm}.}}}} & \left\lbrack {{EQ}.\mspace{14mu} 3} \right\rbrack\end{matrix}$

At the second set point of 20%, Occact=6 (20% of the maximum occupancyof 30 students), S_((0, 1, 2, 3, 4, 5))=1, and the formula is:

$\begin{matrix}{{{\left( {{First}\mspace{14mu} {occupied}\mspace{14mu} {segment}\mspace{14mu} {set}\mspace{14mu} {point}} \right){Rvd}\; 2} = {{\frac{\left\lbrack {\left( {32\text{,}400} \right) + {(6)\left( {10\text{,}000} \right\rbrack}} \right.}{(108) + {(60)(1)}} - 300} = {250\mspace{14mu} {ppm}}}}\mspace{20mu} {{{RV}\; 2} = {550\mspace{14mu} {{ppm}.}}}} & \left\lbrack {{EQ}.\mspace{14mu} 4} \right\rbrack\end{matrix}$

At the third set point of 40%, Occact=12 (40% of the maximum occupancyof 30 students), S_((0, 1, 2, 3, 4, 5))=2, and the formula is:

$\begin{matrix}{{{\left( {{Second}\mspace{14mu} {occupied}\mspace{14mu} {segment}\mspace{14mu} {set}\mspace{14mu} {point}} \right){Rvd}\; 3} = {{\frac{\left\lbrack {\left( {32\text{,}400} \right) + {(12)\left( {10\text{,}000} \right)}} \right\rbrack}{(108) + {60(2)}} - 300} = {368\mspace{14mu} {ppm}}}}\mspace{20mu} {{{RV}\; 3} = {668\mspace{14mu} {{ppm}.}}}} & \left\lbrack {{EQ}.\mspace{14mu} 5} \right\rbrack\end{matrix}$

At the fourth set point of 60% the formula is:

$\begin{matrix}{{{\left( {{Third}\mspace{14mu} {occupied}\mspace{14mu} {segment}\mspace{14mu} {set}\mspace{14mu} {point}} \right){RVd}\; 4} = {{\frac{\left\lbrack {\left( {32\text{,}400} \right) + {(18)\left( {10\text{,}000} \right)}} \right\rbrack}{(108) + {(60)(3)}} - 300} = {438\mspace{14mu} {ppm}}}}\mspace{20mu} {{{RV}\; 4} = {738\mspace{14mu} {{ppm}.}}}} & \left\lbrack {{EQ}.\mspace{14mu} 6} \right\rbrack\end{matrix}$

At the fifth set point of 80% the formula is:

$\begin{matrix}{{{\left( {{Fourth}\mspace{14mu} {occupied}\mspace{14mu} {segment}\mspace{14mu} {set}\mspace{14mu} {point}} \right){RVd}\; 5} = {{\frac{\left\lbrack {\left( {32\text{,}400} \right) + {(24)\left( {10\text{,}000} \right)}} \right\rbrack}{(108) + {60(4)}} - 300} = {438\mspace{14mu} {ppm}}}}\mspace{20mu} {{{RV}\; 5} = {783\mspace{14mu} {{ppm}.}}}} & \left\lbrack {{EQ}.\mspace{14mu} 7} \right\rbrack\end{matrix}$

At the sixth set point of 100%, the formula is:

$\begin{matrix}{{{\left( {{Fifth}\mspace{14mu} {occupied}\mspace{14mu} {segment}\mspace{14mu} {set}\mspace{14mu} {point}} \right){RVd}\; 6} = {{\frac{\left\lbrack {\left( {32\text{,}400} \right) + {(30)\left( {10\text{,}000} \right)}} \right\rbrack}{(108) + {60(5)}} - 300} = {515\mspace{14mu} {ppm}}}}\mspace{20mu} {{{RV}\; 6} = {815\mspace{14mu} {{ppm}.}}}} & \left\lbrack {{EQ}.\mspace{14mu} 8} \right\rbrack\end{matrix}$

With reference to FIG. 3:

-   1. The reset values (RVs) or checkpoints in the IRV graph of FIG. 3    are: RV1=300 ppm CO2; RV2=550 ppm CO2; RV3=668 ppm CO2; RV4=738 ppm    CO2; RV5=783 ppm CO2; RV6=815 ppm CO2.-   2. In the system, when the room is in the ‘occupied-inactive’ mode    at a zero occupancy count (empty room), the outside air control    damper operates to bring in ambient air at approximately Rb=108 cfm    (900 square feet×0.12 cfm/square foot). This air volume, Rb, is    equal to (Vb)(x) and is a constant ventilation flow rate in the    overall equation. If no one is in the room for 5 minutes or more,    the ventilation system goes from the ‘occupied-inactive’ mode to the    ‘unoccupied’ mode and is turned off so there is no ambient    ventilation air flowing into the room. The five minute time element    is adjustable as desired. The minute someone enters the room, the    infrared occupancy sensor (or some other desired sensor) causes    control unit 30 to activate the ‘occupied-active’ mode and control    the dampers 15, 16 to establish the minimum ventilation value, Rb.    As the CO2 concentration rises, the ventilation rate rises to dilute    the CO2 concentration. The amount that dampers 15 and 16 (or 17)    open depends on the difference between the actual CO2 concentration    and the set point RV2, RV3, RV4, etc. The greater the difference,    the more the dampers open.    -   By way of example, if after the dampers are opened to increase        the flow rate of ambient ventilation air, the next reading by        velocity sensor 20B indicates a flow rate of 190 cfm (in the        second segment in FIG. 3) and the CO2 sensor in the room reads        400 ppm (in the first segment in FIG. 3), then control unit 30        begins closing damper 15 to reach an ambient air flow rate that        is in the first segment (108 to 168 cfm) in FIG. 3. The CO2 and        velocity readings preferably are made every three to five        seconds, although this can vary as desired.    -   If in the next reading sensor 20B indicates a flow rate of 175        cfm and the CO2 sensor in the room reads 425 ppm, the control        unit 30 continues to close damper 15 to reach an ambient air        flow rate that is in the first segment toward the goal of        raising room CO2 level to the segment CO2 set point of 550 ppm.    -   If in the next reading sensor 20B indicates a flow rate of 160        cfm and the CO2 sensor reads 425 ppm, the control unit 30        continues to close damper 15 because the CO2 ppm has not reached        550 ppm at set point RV2.    -   If at the next reading sensor 20B indicates a flow rate of 110        cfm and the CO2 sensor reads 560 ppm, then the control unit        begins to open damper 15 to increase the ventilation rate to        reduce the CO2 concentration to 550 ppm or less.    -   If at the next reading sensor 20B indicates a flow rate of 140        cfm and the CO2 sensor reads 450 ppm, then control unit 30        begins again to close the damper 15 since the CO2 concentration        is once again less than 550 ppm. When the damper cfm is in the        first segment (108 to 168), the desired CO2 set point is 550 ppm        (or less). When the damper cfm is in the second segment (168 to        228), the desired CO2 set point is 668 ppm (or less). And so on.    -   If at the next reading, the CO2 ppm in the room is 740 ppm and        the velocity sensor 20B reads 150 cfm, control unit 30 opens        damper 15 to increase the flow of ventilation air.    -   If at the next subsequent reading, the CO2 ppm in the room is        680 ppm and the velocity sensor indicates an ambient air flow        rate of 240 cfm, then the cfm being utilized and the CO2        concentration are each in the third segment (228 to 288) in FIG.        3 and the CO2 set point utilized is the set point for segment        three, namely 738 ppm (or less). In addition, since the CO2        concentration is less than 738 ppm, the control unit 30 begins        to close damper 15 toward the minimum flow rate of 228 cfm for        the third segment.    -   If in the next subsequent reading, the CO2 room sensor indicates        a concentration of 670 ppm, and the velocity sensor 20B        indicates a flow rate of 235 cfm, the control 30 continues to        slowly close damper 15 toward the minimum flow rate of 228 cfm        for the third segment. As long as the ambient air flow (and the        CO2 concentration) is in the third segment, the cfm measured by        sensor 20B should not drop below 228 cfm. And so on.-   3. Within a short period of time, the cfm value and CO2 value    stabilize and the system modulates as necessary to meet the    appropriate room CO2 sensor setpoint RV2, RV3, RV4, RV5, RV6. The    initial set point concentration values for CO2 control are    relatively low and the ventilation system responds immediately,    overshooting the appropriate set point value. Very quickly, within a    minute or so, the room sensor combines with the velocity sensor, in    cfm, to determine which segment is in reference for the CO2 control    set point reset value.-   4. When an individual enters the room, a CO2 sensor in the room    monitors the increase in CO2 above the initial stable RV1=300 ppm in    the room (essentially the ambient air CO2 level) and begins to open    the outside air damper to increase the amount of ventilation air    entering the room. The first ‘active’ occupied CO2 concentration    checkpoint RV2 is 250 ppm above ambient or 550 ppm total.-   4. As the outside air damper opens, the velocity sensor in the air    stream registers the increase in air flow and sends the value to the    control unit 30 to determine into which segment air flow value the    air quantity registers.-   5. Since one individual will generate a CO2 amount requiring    approximately 10 cfm of outside air for dilution to 700 ppm above    ambient, approximately 6 students can enter into the room at the    first segment upper CO2 limit RVd2 of 250 ppm above ambient. The 6    student load is coincidental with the first segment maximum air flow    rate of [(Vp)(Occact)+(Va)(x)], as it should be. The total outside    air entering the room at this segment limit is 108 cfm (area    ventilation rate)+60 cfm (people ventilation rate)=168 cfm total    ventilation rate.-   6. During all modes of area occupancy (when the first person enters    the room), the initial checkpoint or segment target CO2 value RVd2    added to the OSACO2 will be the first segment CO2 limit RV2. The    only time the 300 ppm total RV1 (or 0 ppm above ambient)    concentration will occur is when the room is unoccupied. The minute    a person enters, the first segment value will define the limits    until its maximum segment air flow value in cfm is exceeded. By way    of example, the maximum air flow for segment one is, in the example    set forth in FIG. 3, 168 cfm. The maximum air flow for segment two    is 228 cfm.-   7. As additional students enter the room, the CO2 sensor will    register a coincidental rise in the CO2 concentration and the    control unit 30 will open the outside air damper 15 further if the    CO2 concentration exceeds the set or check point value RV2, RV3,    etc. associated with the segment in which the damper ventilation    rate is operating. When the ventilation rate exceeds the first    segment 168 cfm value, which also defines the upper limit of the    first segment CO2 value (i.e., 550 ppm), the measured air quantity    enters into the region of the second segment, which defines an upper    air flow rate of 228 cfm and a CO2 concentration upper limit of 368    ppm above the ambient air CO2 concentration, or, as is shown in FIG.    3, a total CO2 concentration RV3 of 668 ppm.-   8. The ‘five segment’ calculation example created above defines the    air flow rates and CO2 concentration limits of each segment. It does    not control the space CO2. The space CO2 is limited by the CO2    sensor in the room and the operation of the outside air control    dampers. The calculation accumulates the sensed outside air quantity    and redefines the CO2 sensor set point, nothing more. However, this    is the most critical part of Indoor Air Quality management,    maintaining the proper CO2 limits with a moving occupant ventilation    rate target combined with a fixed area ventilation rate.-   9. As additional students enter the room and the CO2 concentration    rises and the ambient air input damper 15 is opened further, a    greater outside air quantity is measured by the velocity sensor. As    the velocity sensor value in cfm continues to change, it will    register into any one of the segment air value limits. When the CO2    sensor takes a reading and transmits its value to the control unit    30, the control unit 30 will look at the air quantity recorded at    the velocity sensor, determine which segment it falls into, and    compare the segment CO2 limit to the CO2 concentration sensed. The    controller will send a signal to the outside air control damper to    increase or decrease the air to the room to meet the segment set    point RV2, RV3, RV4, RV5, RV6. Then, as the sensed air quantity    continues to change, in response to the generation of CO2 (or to a    decrease in CO2 when children leave the room) in the space, it will    redefine which segment is applicable and redefine the CO2 limit as    necessary. This is a dynamic function. CO2 measurements are taken,    air flow rates are adjusted, CO2 measurements are taken, all the    while, the calculations continue to reset the CO2 concentration    target.-   10. And so on.

Because measurements are taken constantly, it is not a good controlscenario to make continuous adjustments because the control dampers will‘hunt’ for a control point and never achieve it. Creating segments,where the CO2 target value is fixed for more than a minute amount ofchange of air quantity, allows for a more stable control of outside airquantity and helps prevent rapid cycling of air conditioning equipmentin an attempt to meet a room temperature set point with a ‘wild’ mixedair temperature entering the cooling or heating coils or furnace.

Discussion of Formula

Since actual numbers sometimes aide understanding a calculation process,the values used in the above example are referenced in the followingdiscussion.

This particular method of controlling the flow of ventilation air into aroom is to continuously ventilate a room with ambient air at a base rateequivalent to the Area Outdoor Air Rate set forth in ASHRAE 62.1-2010:Table 6.1, and to increase the ventilation rate whenever an individualenters the room, and to decrease the ventilation rate whenever anindividual leaves the room. For each person entering the room, theventilation rate is increased to meet an approximate air quantity basedon the People Outdoor Air Rate set forth in ASHRAE 62.1-2010: Table 6.1.In the above example, the People Outdoor Air Rate for an individual is10 cfm. The 10 cfm value per person was set by ASHRAE 62.1-2010 aftercompleting several studies which determined that for children 5-8 yearsof age, taking into account their volumetric CO2 generation and theiractivity levels, that it takes approximately 10 cfm per person toproperly dilute the space CO2 to 700 ppm above ambient. 700 ppm aboveambient CO2 is recognized by ASHRAE as the target CO2 concentration tominimize objectionable odor recognition for 80%+of occupants newlyentering a space who have not become acclimated to the people generatedodors of the space. Therefore, for the sake of this particular examplecalculation, it will be established that for approximately each 10 cfmof air entering the area through the outside air control damper, onestudent will be accounted for in the ventilation calculation. ASHRAE isthe American Society of Heating, Refrigerating, and Air ConditioningEngineers.

Stated for this calculation, the base ventilation rate is (x)(Va), whichin the above example is (900 sq ft)(0.12 cfm/sq. ft)=108 cfm. The systemwould, consequently, ventilate an empty room at 108 cfm. When the firstperson enters the room, the ventilation rate is increased by 10 cfm to118 cfm. When the second person enters the room, the ventilation rate isincreased to 128 cfm, and so on. Each time a person leaves the room, theventilation rate is decreased by approximately 10 cfm.

Establishing that this control method utilizes the formula set forthabove to control the ventilation of a room with ambient air, the formulacalculates for set checkpoints at desired CO2 levels in the room abovethe CO2 level in the ambient air.

Examining the formula further, each air stream ventilation rate has itsactual or maximum allowable CO2 concentration attribute. The areaventilation rate air stream contributes to the equation 108 cfm of 300ppm CO2 concentration. This would be like comparing 108 gallons of waterper minute at 300 degrees F. (under high pressure of course). The peopleventilation rate air stream CO2 contribution to the equation includesthe base 300 ppm of CO2 and allows for an additional 700 ppm CO2increase. The people ventilation rate contributes 1000 ppm CO2 (total)for each cfm of air. When we are establishing the maximum allowable CO2concentration at its specific target cfm limit, we know that the 300 ppmCO2 air stream will dilute the 1.000 ppm CO2 air stream. We are addingthe air stream CO2 values to quantify the assimilation of the total CO2into the total of the two air streams and determine the influence of theambient CO2 air quantity on the room generated CO2. Once assimilated,the resultant CO2 concentration should represent the discounted CO2value, which achieves the ASHRAE defined individual ventilation air flowrate requirements for area and people.

In general, the formula has to take into account ventilation air flowinto the room for two purposes:

-   -   1. Area ventilation of the room. The area ventilation air flow        rate is determined using the Area Outdoor Air Rate Va set forth        in ASHRAE Table 6.1 and using the size of the room in square        feet.    -   2. Ventilation air to compensate for additional CO2 produced        when individuals are in the room. This people ventilation air        flow rate is determined using the People Outdoor Air Rate Vp set        forth in ASHRAE Table 6.1 and the number of people in the room.

A. Area Ventilation Air Flow Rate for the Room

-   -   This ventilation rate is represented in the formula by:

[(CRT or HRT)(x)(Va)

-   -   And, when CRT or HRT and Altcorr each equal one, this becomes:        (x)(Va)

B. Ventilation Air Flow Rate for People

-   -   This ventilation rate is represented in the formula by:

(Vp)(Occmax)

C. Calculation of an IRVcfm.

The cfm of ventilation air is, as noted, physically measured todetermine the cfm location on the horizontal axis of an IRV graph. Themaximum cfm of a segment (i.e., the IRVcfm) is, on the IRV graph,associated with an RV. When the IRVcfm of an RV is reached or exceeded,as determined by the physical measurement of the incoming ventilationair in cfm, the next IRVcfm is selected.

One method of calculating an IRVcfm adding the base room areaventilation, Rb, to the ventilation for the number of people in a room,(Occact)(Vp). These terms are seen in EQ. 1 described above.

A second method of calculating an IRVcfm is to add the base rrom areaventilation to a calculation in which the total or maximum peopleventilation rate of (Vp)(Occmax) is divided by the number of segments,n, and multiplied by the number of segments, (S_((0, 1, 2, 3, 4, 5))),which are, when moving from left to right on the horizontal axis of anIRV graph from the base area ventilation rate in cfm, required to reachthe IRVcfm at issue.

Therefore, an IRVcfm=[(Vp)(Occmax)/n](S _((0, 1, 2, 3, 4, 5)))

Using either the first or the second method of calculating an IRVcfmgives the same result.

The block flow diagram of FIG. 4 illustrates an embodiment of aventilation system that can be utilized in the practice of theinvention. The system includes a computer which can be utilized in thecontrol unit 30 of ventilation unit 10. The computer includes controller62 and memory 64. The computer can be a digital computer, analogcomputer, hybrid computer, or other programmable apparatus. In practice,the very large majority of computers comprise digital computers.

The memory 64 can be any suitable prior art memory unit such as arecommonly used in digital or other computers. For example,electromagnetic memories such as magnetic, optical, solid state, etc. ormechanical memories such as paper tape.

Velocity sensor(s) 62, indoor and outdoor CO2 sensors 55, and roomthermostat 54 input data to memory 64, and can also input the data tocontroller 63. An outdoor temperature sensor, room temperature sensor,and indoor occupancy sensor, or any other desired sensor or data inputmeans can also be utilized to input data to memory 64 or controller 63.

Controller 63 includes IRVcfm calculation sub-routine 50, RV calculationsub-routine 51, and damper adjustment sub-routine 52. IRVcfm calculationsub-routine 50 utilizes variables n, Vp, Va, x, Occmax input 56 frommemory. RV calculation sub-routine 51 utilizes EQ 1 above (ControlSystem Ventilation Formula) and the variables 57 from memory 64including n, Vp, Va, x, Ocmax, Occact, CO2max, CRT, HRT, Altcorr,S_((0, 1, 2, 3 . . . n)), and OSACO2 to calculate RV values like thoseon the graph of FIG. 3. The damper adjustment sub-routine 52 utilizesvariables 58 from memory 64 including Vamb (the desired velocity ofincoming air to achieve the desired ppm CO2 (RV1, RV2, etc.) at the cfmcheckpoints (108 cfm, 168 cfm, etc.) on the graph of FIG. 3. Oncecontrol 61 utilizes sub-routine 52 to calculate the desired cfm, control61 transmits the necessary signals to damper(s) 54 to achieve thedesired cfm of incoming ventilation air.

FIG. 5 is a block flow diagram which illustrates a typical program orlogic function which is executed by the controller 63. The basic controlprogram consists of commands to “start and initialize” 70, “read memory”71, and “transfer control” 72 sequentially to one of subroutines 50 to52. Each sub-routine 50 to 52 includes the steps of “interpret memory”75, “perform the sub-routine function(s)” 76 (i.e., determine IRVcfm,RV. etc.), followed by “return to control program” 77. The sub-routinesare repeated as indicated by the “repeat to last memory step” 73,followed by an “end” 74 program step which completes the execution ofthe program.

Control unit 30 controls the flow rate in cfm of ventilation air throughunit 10 by opening and closing dampers 15, 16, 17. Fans 13 and 14increase or decrease their flow volumes based on a static pressuresensor in the outside air duct or the exhaust air duct. A variable speedmotor controller increases or reduces the fan speed to maintain aselected static pressure set point. The control unit 30 changes thespeed of the fan motors to try maintain a static pressure level in eachduct.

An alternate embodiment of the invention is illustrated in FIGS. 6 and7. In FIGS. 6 and 7, D10 is an air duct integrated with duct D30 forreturn air to air conditioner 220; D20 is an air duct directing cooled(or heated) supply air S10 from air conditioner 220 back to the room;D30 is a duct through which return air from the room flows in unit 100;D40 is a duct that directs return air into the coil/fan section of airconditioner 220; D50 is a duct that directs ambient air A10 into unit100 and into one side of heat exchange unit 120 and between and throughfinned layers comprising unit 120; D60 is a duct that directsexhaust/relief air from heat exchange unit 120 into the ambientatmosphere; A10 and A20 are ambient air streams flowing into duct D50;A10 is a fan induced ambient air stream directed through or over heatexchange unit 120; A20 is a fan induced ambient air stream that bypassesheat exchange unit 120 and travels through duct D50 and unit 100 tojoint return air stream R10 in the manner illustrated in FIG. 7; and R20is a portion of the return air stream that is drawn over or through heatexchange unit 120. In FIG. 7, S10 is a combination of return air R10 andoutside ambient air A20. In FIG. 6, S10 is a combination of a portionR10 of the return air and of ambient air A10 that has passed throughheat exchange unit 120. In FIG. 6, portion R20 of the return air passesthrough heat exchange unit 120 and out through duct D60. FIG. 7 does notcall out a portion R20 because portion R20 is zero, i.e., in FIG. 7 noneof the return air stream is directed through heat exchange unit 120. InFIG. 7, portion R10 comprises the entire return air stream, minus reliefair which exits the room to outside the building through normal buildingrelief air paths.

FIG. 6 illustrates the heat recovery mode of the ventilation system ofthe invention. FIG. 7 illustrates the economizer mode of the ventilationsystem of the invention. In the economizer mode, the temperature of theambient air stream A20 permits it to be added directly to the return airstream R10 and obviates the necessity of passing an ambient air streamA10 over or through heat exchange unit 120.

In the embodiment of the invention illustrated in FIGS. 1 and 2, airstreams A1 and R2 must make ninety degree turns while traversingventilation unit 10. Air stream A1 makes a ninety degree turn to enterheat exchange unit 12. Air stream R2 makes a ninety degree turn afterexiting heat exchange unit 12. Such ninety degree turns produceincreased upstream pressure and increase the energy required for airstreams A1 and R2 to pass through ventilation unit 10. In contrast, inFIGS. 6 and 7, air streams A10 and R20 need not make ninety degreesturns to while entering or exiting, respectively, heat exchange unit120. Heat exchange unit 120 is rotated such that its faces are canted atangles less than ninety degrees with respect to walls 80 and 81 (FIG.11). Air stream A10 need not make a ninety turn to enter unit 120. Thisdecreases the energy consumed by air streams A10 and R20 while passingthrough ventilation unit 100.

In FIG. 6, damper assembly 150 is in a first open operative positionwhich permits air stream A10 to flow through duct D50, through the leftside of damper assembly 150, and into heat exchange unit 120. Whenangled damper blade 38 is in the first open operative position, airstream A20 is prevented from flowing into duct D50, through the rightside of damper assembly 150, and into duct D10 along a path to the rightof heat exchange unit 120 to join return air stream R10 in the mannerillustrated in FIG. 7. Air stream A20 is produced only when damper blade38 is in the second open operative position illustrated in FIG. 7. Whendamper blade 38 is in the second open operative position, air stream A10is not produced because damper blade 38 blocks the path of travelillustrated in FIG. 6. When damper blade 38 is in the first openoperative position, air stream A20 is not produced because damper blade38 blocks the path of travel illustrated in FIG. 7.

When portion R20 of the return air stream travels through heat exchangeunit 120 in the manner illustrated in FIG. 6, damper assembly 160 is ina first open operative position which permits air stream R20 to exitthrough duct D60. Alternatively, when a portion R20 of the return airstream does not pass through heat exchange unit 120, damper assembly 160is in the second closed operative position illustrated in FIG. 7. Damperassemblies 150 and 160 each rotate or pivot about shafts 31 and 32,respectively (FIGS. 6 and 7).

FIGS. 8A, 8B, and 8C further illustrate three general operativepositions of damper 150. In FIG. 8C, damper assembly 150 is in a thirdclosed operative position which prevents ambient air from flowing intoand through duct D50 and past damper 150. In FIG. 8B, damper assembly150 is rotated from the third closed operative position of FIG. 8C inthe direction of arrow B (FIG. 8B) to the second open operative positionallowing ambient air to follow the path indicated by arrow A20 in FIG.8B and FIG. 7. In FIG. 8A, damper assembly 150 is rotated from the thirdclosed operative position of FIG. 8C in the direction of arrow A (FIG.8A) to the first open operative position allowing ambient air to followthe path indicated by arrow A10 in FIG. 8A and FIG. 6. As would beappreciated by those of skill in the art, damper assembly 150 can berotated (1) from the second open operative position through the thirdclosed operative position to the first open operative position, and viceversa, (2) from the second open operative position back to the thirdclosed operative position, and (3) from the first open operativeposition back to the third closed operative position. The majority ofthe time, damper assembly 150 will be in either the first or second openoperative position.

The particular location of damper blade 38 when it is in the first (orsecond) open operative position is determined by the algorithm earlierdescribed herein. The algorithm determines at any given instant in timea desired flow rate of air, either into the heat exchange unit 120 viathe airflow path generally located by arrow A10 or bypassing heatexchange unit 120 via the air flow path generally located by arrow A20.As is indicated in FIG. 11, once controller 300 determines that damperblade 38 needs to be operated in, for example, the second operativeposition of FIG. 8B, controller 300 is using the previously describedalgorithm (or another desired algorithm) to continuously calculate adesired flow rate of air, and send signals to motor 86 to adjust theposition of damper blade 38 to increase or decrease the flow rate of airalong the path generally indicated by arrow A20 (FIG. 7). Motor 86 turnsshaft 31, and therefore damper blade 38 and shaft 31, in the directionof arrow B or in a direction opposite that of arrow B. Minuteadjustments of the damper blade 38 rotation in damper assembly 150 willcontinue to occur to meet the algorithm calculated air flow raterequirements.

FIG. 9 is a top (plan) view illustrating construction details of damperassembly 150 and its operatively associated divider panel 35. Whenambient air is traveling along the path indicated by arrow A20, panel 35(along with associated circumscribing walls of duct D50) preventsambient air from crossing over into the path that is followed by airtraveling along a path indicated by arrow A10. When ambient air istraveling along the path indicated by arrow A10, panel 35 (along withthe associated circumscribing walls of duct D50) prevents ambient airfrom crossing over into the path that is followed by air traveling asindicated by arrow. A20.

Damper assembly 150 includes drum arc segments 39A and 39B withscalloped edges 63A and 63B, and solid contoured panels 64A and 64B(FIGS. 11 and 13). Damper assembly 150 also includes a slotted topgenerally circular panel 36 and a slotted bottom generally circularpanel 37. The shape and dimension of panel 36 is presently equivalent tothat of panel 37, although that need not be the case. Angled damperblade 38 extends between and interconnects spaced apart, scalloped edgedrum arc segments 39A and 39B (FIG. 9). As is illustrated in FIG. 13,contoured panels 64A and 64B extend from the interior scalloped edges63A and 63B approximately 60 degrees away from the scalloped edges,finishing with a linear edge which is perpendicular to the slotted drumtop 36 and slotted drum bottom 37. Damper assembly 150 can be formed inany desired manner and can comprise a solid piece of material. It ispresently preferred that damper assembly 150 be fabricated from sheetmetal or sheet plastic in order to reduce the amount of material andweight required to produce a system in accordance with the invention.Any desired system can be devised to seal appropriately the peripheraledges of angled damper blade 38 to prevent air from flowing betweendamper blade 38 and scalloped drum segments 39A and 39B unless damperblade 38 is in the first or second open operative position. In FIG. 12,for example, elongated fixed neoprene or rubber edge gaskets 84A and 84Bsealingly engage the top 36 and bottom 37 of the damper assembly 150,and elongated neoprene or rubber edge seals or gaskets 85A, 85Bsealingly engage portions of drum segments 63A and 63B. In FIG. 11, andenhanced in FIG. 12, angled damper blade 38 is in the third closedoperative position. In the third operative position, the entire lengthof each straight/perpendicular edge 84A and 84B and 85A and 85B is incontact with the interior solid, contoured or flat surfaces of thedamper assembly 150 so that air cannot enter duct D50 and flow pastdamper assembly 150. Edge seals/gaskets 84A and 84B are fixedly attachedto the top and bottom of angled damper blade 38 and seals/gaskets 85Aand 85B are fixedly attached to the sides of angled damper blade 38.Bushings/bearings 69 and 68 sealingly engage shaft 31. Edgeseals/gaskets 84A and 84B sealingly slide against slotted top and bottom36 and 37, respectively. Edge seals/gaskets 85A and 85B sealingly slideagainst scalloped drum arcs 39A and 39B contoured interior surfaces

FIG. 12 depicts how rotatable shaft 31 can extend completely through andbe fixedly attached to angled damper blade 38. Rotatable shaft 31 can bedrilled and tapped axially in angles separated by 120 degrees to matchthe angle of the damper blade. Threaded, locking screws or bolts canengage the tapped and threaded shaft openings, from the blade side ofthe shaft, to a maximum of 75% of the threaded depth to secure the bladeto the shaft at a minimum of three places per angled surface.

As can be seen in FIGS. 8C and 9, blade segments 33 and 34 of angleddamper blade 38 are not co-linear, but instead together form an innerobtuse angle of less than one hundred and eighty degrees, typicallypresently about 120 degrees. This provides space for scalloped drumsegments 39A and 39B such that in FIGS. 8C and 9, edges 85A and 85B ofdamper blade segments 33 and 34 are in their entirety on the solidcontoured, not scalloped, inner surfaces of drum arc segments 64A and64B. In FIG. 8A, angled damper blade 38 will rotate from the thirdoperative position through an arc having a length of between 0 degreesand 60 degrees toward the first operative position, allowing increasingair flow amounts to pass through the scalloped opening 63A of drumsegment 39A in direction of air flow A10. Similarly for FIG. 8B, angleddamper blade 38 will rotate from the third operative position through anarc of between 0 degrees and 60 degrees toward the second operativeposition, allowing increasing air flow amounts to pass through thescalloped opening 63B of drum segment 39B in direction of air flow A20.

During normal operation of shaft 31 and motor 86, when damper blade 38is in the first operative position of FIG. 8A, damper blade segment 34maintains contact with drum segment 64B and does not rotate past theperpendicular edge 64C (FIG. 11) of drum segment arc 64B. In FIG. 8A,damper blade 38 has rotated clockwise from the position of FIG. 8Cthrough its greatest possible arc of travel and is in a first “fullyopen” position. Similarly, during normal operation of shaft 31 and motor86, when damper 38 is in the second operative position of FIG. 8B,damper blade segment 33 maintains contact with drum segment 64A and doesnot rotate past the perpendicular edge 64D (FIG. 11) of drum segment arc64A. In FIG. 8B, damper blade 38 has rotated counterclockwise from theposition of FIG. 8C through its greatest possible arc of travel and isin a second “fully open” position.

The diameter, indicated by arrows F in FIG. 13, of damper 150 ispresently ten inches, and the height, indicated by arrows G in FIG. 13,of damper 150 is presently sixteen inches. In the majority of cases, thediameter of damper 150 will be in the range of nine to eleven inches,and the height of damper 150 will be in the range of fifteen toseventeen inches. The diameter of damper 150 may, however, be in therange of six to twelve inches and the height of damper may be in therange of sixteen to thirty inches. The diameter and height of damper 150are varied to meet desired air flow requirements, to meet sizingrequirements of ducting and air conditioning units, and/or to meet otherdesign criteria.

The referenced 10 inches diameter by 16 inches high damper assembly 150has a generally cylindrical shape and includes two contoured panels 64A,64B each with a scalloped edge 63A, 63B, respectively, which edge 63A,63B provides a control surface for damper blade 38 to regulate air flowthrough one side of the damper module while damper blade 38 prevents airflow through the other side of the damper module. The contoured panels64A, 64B of damper 150 each are configured with a 10 inches diameter,and extend through a 120 degree long arc. The 120 degree long arcincludes a scalloped edge 63A, 63B which extends through a 60 degreelong arc, and, also includes an arcuate solid panel with a verticalcut-off 64C, 64D (FIG. 11) which is perpendicular to the top and bottomof the drum. The solid panel extends through a 60 degree long arc. Eachscalloped edge 63A, 63B is exposed to the air stream in varying amountsto allow regulation of air flow through the open areas in edge 63A, 63Busing damper blade 38 in its varying positions contacting a solidportion of the scalloped segment arc length.

The top 36 and bottom 37 of the damper assembly 150 are comprised ofgenerally circular discs which are furnished with openings of therequired size in the center of the discs. The openings are used toinstall the actuator shaft bushings/bearings 68 and 69. A slot isprovided in each of the top 36 and bottom 37 disc to install the airdiverter partition 35, FIG. 15. The air diverter partition separates thetwo air streams of A10 and A20 as required for the first operativeposition and the second operative position respectively of damper blade38. Further, air diverter partition 35 extends through the top 36 andbottom 37 and attaches to the inside top and bottom of duct module D50.Air diverter partition 35 is attached to the top 36 and bottom 37 andsealed to prevent air leakage between first operative position airstream A10 and second operative position air stream A20.

When damper assembly 150 is in the economizer mode illustrated in FIG.8B, the position of damper blade 38 is, for a damper assembly 150 with adiameter of ten inches and a height of sixteen inches, adjusted to varythe air flow A20 between 100 cfm (cubic feet per minute) and 700 cfm.When the damper assembly 150 is in the heat recovery mode illustrated inFIG. 8A, the position of damper blade 38 is, for a damper assembly 150with a diameter of ten inches and a height of sixteen inches, adjustedto vary the air flow A10 between 100 cfm and 450 cfm. One way toincrease the airflow A10 or A20 for a given amount of revolution ofdamper blade 38 is to make the damper assembly 150 taller. Another wayto increase the airflow A10 or A20 for a given amount of revolution ofdamper blade 38 is to increase the diameter of the damper assembly 150.Still another way to increase the airflow A10 or A20 for a given amountof revolution of damper blade 38 is to reduce the height of damperassembly 150 and increase the diameter of the damper assembly 150 by adesired amount. Yet another way to increase the airflow of damper blade38 is to increase the height and diameter of damper assembly 150. Andyet another way to increase the airflow of damper assembly 150 is tochange the scallop contours of arc segments 63A and 63B as illustratedby 42A, 42B, 42C, 42E, etc., FIG. 10. Reducing the airflow of damperassembly 150 is accomplished by carrying out the reverse of theforegoing size increasing procedures. The minimal desired airflow A10 orA20 into a classroom is typically 100 cfm.

The airflow A20 in the economizer mode of FIG. 8B is increased byrotating damper blade 38 and shaft 31 in the direction of arrow B (FIG.8C). The incorporation in scalloped edge 63B of arcuate edge segments40, 41, 43, 44 and 42, 42A, 42B, 42C, 42D or 42E, FIG. 9 is important inthis respect because with each degree of rotation of damper assembly 150in the direction of arrow B, the amount of increase in airflow A20 isless than if edge segments 40, 41, 43, 44 and 42, 42A, 42B, 42C, 42D or42E were straight and parallel to edge 85B of damper blade 38. Therotational centerline of damper blade 38 is the centerline through shaft31. As damper blade 38 begins to open to permit airflow A20, suchairflow A20 initially can pass only through the open areas 40A and 41Aof “valleys” 40 and 41 (FIG. 10) of edge 63B. This facilitates beingable to adjust the airflow in small increments. In the practice of theinvention, it is important to be able to adjust the airflow byincrements at least as small as one to two percent of the maximumairflow in the heat recovery mode and the economizer mode. Consequently,for example, if the maximum airflow in the economizer mode is 700 cfm,it is important to be able to adjust the air flow by 7 to 14 cfm.Scalloped edge 63B facilitates such airflow adjustments.

The airflow A10 in the heat recovery mode of FIG. 8A is increased byrotating damper blade 38 and shaft 31 in the direction of arrow A (FIG.8C). The incorporation in scalloped edge 63A of arcuate edge segmentscomparable to those illustrated in FIG. 10 for edge 63B is important inthis respect because with each degree of rotation of damper 150 in thedirection of arrow A, the amount of increase in airflow A10 is less thanif said arcuate edge segments were straight and parallel to edge 85A ofdamper blade 38. The rotational centerline of damper blade 38 is thecenterline through shaft 31. As damper blade 38 begins to open to permitairflow A10, such airflow A10 initially can pass only through the openareas of “valleys” of edge 63A. This facilitates being able to adjustthe airflow in small increments. In the practice of the invention, it isimportant to be able to adjust the airflow by increments at least assmall as one to two percent of the maximum airflow in the heat recoverymode and the economizer mode. Consequently, for example, if the maximumairflow in the heat recovery mode is 450 cfm, it is important to be ableto adjust the air flow by four and one-half to nine cfm. Scalloped edge63A facilitates such airflow adjustments.

The shape and dimension of scalloped edges 63A and 63B can vary asdesired. The presently preferred design of edges 63A and 63B utilizesvalleys 40 and 41 and peaks 42 which each correspond to one-half(valleys 40 and 41, and peak 42) or one-quarter (peaks 43 and 44) of theshape of an ellipse. The number and shape of such peaks and valleys canvary as desired. For example, valleys 40 and 41 may have a circularcontour; or, an edge 63A can have a saw tooth configuration. One or moreopenings, such as the opening depicted by dashed line 92 in FIGS. 10 and13, can be formed though damper arc segments 39A or 39B near an edge 63Aor 63B respectively.

In one embodiment of the invention the diameter and/or height of damperassembly 150 is decreased sufficiently such that the air flow in theeconomizer mode is 70 to 450 cfm; and, the air flow in the heat recoverymode is 70 to 300 cfm.

In another embodiment of the invention, the diameter and/or height ofdamper assembly 150 is increased sufficiently such that the air flow A20in the economizer mode is 150 to 2100 cfm; and, the air flow A10 in theenergy recovery mode is in the range of 70 to 1400 cfm.

The diameter of damper assembly 150 typically corresponds to the widthof the plenum D50 of DVHR module 100. The height of damper assembly 150presently typically generally corresponds to the height of the heatexchange unit 120.

Accordingly, in general, during the practice of the invention, theairflow A20 in the economizer mode can be in the range of 70 to 2100cfm, and the airflow A10 in the heat recovery mode can be in the rangeof 70 to 1400 cfm.

The maximum possible airflow during the economizer mode is always begreater than the maximum possible airflow during the heat recovery mode.

In FIG. 11, motor 86 is utilized to rotate shaft 31, and thereforedamper blade 38, in the direction of arrow A and in a direction oppositethat of arrow A. Motor 86 can be a stepper motor or an infinitelymodulating motor. Motor 86 preferably is able to rotate damper blade 38in increments at least as small as 0.1 degree.

A particular advantage of the damper blade 38 is that it enables smallincremental changes in air flow while at the same time enabling andcontrolling the modulation of two separate airflows A10 and A20. AirflowA10 is modulated independently of airflow A20. If airflow A10 is beingutilized during operation of the system of the invention, airflow A20 isnot being utilized, and vice versa.

One goal of the invention is to make the increase in airflow A10 or A20linear with respect to the amount of rotation of damper blade 38. Asdamper blade 38 is rotated to permit airflow A10 or A20 to increase, thecross-sectional area through which airflow A10 or A20 moves increasesalong with the perimeter of the cross-sectional area. Preferably, thecross-sectional area should change proportionally to the perimeter ofthe cross-sectional area to permit linear, or substantially linear,control of the volume of air passing through the cross sectional area.Ideally, a given increase in the cross-sectional area produces a likeincrease in the perimeter of the cross-sectional area, e.g., a 10%increase in cross-sectional area produces a 10% increase in theperimeter of the cross-sectional area.

In the presently preferred embodiment of the invention, damper blade 38is rotated a maximum of 60 degrees from the third operative position ofFIG. 8A in the direction of arrow A; and, similarly is rotated a maximumof 60 degrees from the third operative position of FIG. 8A in thedirection of arrow B. Such maximum rotation values can be adjusted asdesired.

In FIG. 8B, the cross-sectional area through which airflow A20 moves isbounded by the edge of damper blade seal 85B of damper blade segment 34(FIG. 9), edge 63B of drum arc segment 63B, and top seal 84A and bottomseal 84B (FIG. 12). In FIG. 8A, the cross-sectional area through whichairflow A10 moves is bounded by the edge of damper blade seal 85A ofdamper blade segment 33 (FIG. 9), edge 63A of drum arc segment 63A, andtop seal 84A and bottom seal 84B (FIG. 12). When damper blade 38 isrotated to increase the flow of air through one of these cross-sectionalareas, the pressure drop produced by the air as it moves through thecross-sectional areas decreases. If there is a pressure drop reductionproduced when air flow A10 moves past damper 38, then there is acorresponding increase in the pressure drop produced as the air passesthrough heat exchange unit 120.

In addition to being utilized in connection with air conditioning(heating/cooling) systems, damper assembly 150 can be utilized in anyatmospheric pressure gas/vapor regulating system which requires thedivision and modulation of a single gas/vapor stream into two separateindependent gas/vapor streams.

While damper assembly 150 and other system components can be fabricatedfrom any desired material, it is presently preferred that damperassembly 150 be constructed from a medium to high strength material suchas, for example, carbon steel, aluminum, polymer or other materials. Theparticular material selected will depend on system pressures,corrosivity of the gas/vapor, and the maximum allowable smoke spread andflame development requirements of NFPA and local building codes. Thepreferred maximum leakage for seals 85A and 85B (FIG. 12) in an airconditioning system when damper blade 38 is in the third operativeposition is 2% of the design air flow at a system pressure of threeinches water column pressure.

Motor 86, or any other desired actuator system, is preferably a lowvoltage (less than 115 volts) or line voltage (115 volts to 600 volts)motor capable of rotating shaft 31 through a minimum of 180 degrees ofrotation, and includes a position feedback that can recognize whendamper blade 38 is in the third operative position (shut off position)of FIG. 8C and can recognize any other desired position of damper blade38. Alternate position sensing systems can be utilized, such as amagnetic end switch device attached to damper blade 38 and either thetop drum disc 36 or bottom drum disc 37.

Still another embodiment of the invention is illustrated in FIGS. 16 and17. In FIGS. 16 and 17, D10 is an air duct integrated with duct D30 forreturn air to air conditioner 220; D20 is an air duct directing cooled(or heated) supply air S10 from air conditioner 220 back to the room;D30 is a duct through which return air from the room flows in unit 100;D40 is a duct that directs return air into the coil/fan section of airconditioner 220; D50 is a duct that directs ambient air A10 into unit100 and into one side of heat exchange unit 120 and between and throughfinned layers comprising unit 120; D60 is a duct that directsexhaust/relief air from heat exchange unit 120 into the ambientatmosphere; A10 and A20 are ambient air streams flowing into duct D50;A10 is a fan induced ambient air stream directed through or over heatexchange unit 120; A20 is a fan induced ambient air stream that bypassesheat exchange unit 120 and travels through duct D50 and unit 100 tojoint return air stream R10 in the manner illustrated in FIG. 17; andR20 is a portion of the return air stream that is drawn over or throughheat exchange unit 120. In FIG. 17, S10 is a combination of return airR10 and outside ambient air A20. In FIG. 16, S10 is a combination of aportion R10 of the return air and of ambient air A10 that has passedthrough heat exchange unit 120. In FIG. 16, portion R20 of the returnair passes through heat exchange unit 120 and out through duct D60. FIG.17 does not call out a portion R20 because portion R20 is zero, i.e., inFIG. 17 none of the return air stream is directed through heat exchangeunit 120. In FIG. 17, portion R10 comprises the entire return airstream, minus relief air which exits the room to outside the buildingthrough normal building relief air paths.

FIG. 16 illustrates the heat recovery mode of the ventilation system ofthe invention. FIG. 17 illustrates the economizer mode of theventilation system of the invention. In the economizer mode, thetemperature of the ambient air stream A20 permits it to be addeddirectly to the return air stream R10 and obviates the necessity ofpassing an ambient air stream A10 over or through heat exchange unit120.

In the embodiment of the invention illustrated in FIGS. 1 and 2, airstreams A1 and R2 must make ninety degree turns while traversingventilation unit 10. Air stream A1 makes a ninety degree turn to enterheat exchange unit 12. Air stream R2 makes a ninety degree turn afterexiting heat exchange unit 12. Such ninety degree turns produceincreased upstream pressure and increase the energy required for airstreams A1 and R2 to pass through ventilation unit 10. In contrast, inFIGS. 16 and 17, air streams A10 and R20 need not make ninety degreesturns to while entering or exiting, respectively, heat exchange unit120. Heat exchange unit 120 is rotated such that its faces are canted atangles less than ninety degrees with respect to walls 80 and 81 (FIG.21). Air stream A10 need not make a ninety turn to enter unit 120. Thisdecreases the energy consumed by air streams A10 and R20 while passingthrough ventilation unit 100.

In FIG. 16, damper assembly 1150 is in a first open operative positionwhich permits air stream A10 to flow through duct D50, past the leftedge of damper assembly 1150, and into heat exchange unit 120. Whendamper assembly 1150 is in the first open operative position, air streamA20 is prevented from flowing into duct D50, past the right edge ofdamper assembly 1150, and into duct D10 along a path to the right ofheat exchange unit 120 to join return air stream R10 in the mannerillustrated in FIG. 17. Air stream A20 is produced only when damperassembly 1150 is in the second open operative position illustrated inFIG. 17. When damper assembly 1150 is in the second open operativeposition, air stream A10 is not produced because damper assembly 1150blocks the path of travel illustrated in FIG. 16. When damper assembly1150 is in the first open operative position, air stream A20 is notproduced because damper assembly 1150 blocks the path of travelillustrated in FIG. 17.

When portion R20 of the return air stream travels through heat exchangeunit 120 in the manner illustrated in FIG. 16, damper assembly 1160 isin a first open operative position which permits air stream R20 to exitthrough duct D60. Alternatively, when a portion R20 of the return airstream does not pass through heat exchange unit 120, damper assembly1160 is in the second closed operative position illustrated in FIG. 17.Damper assemblies 1150 and 1160 each rotate or pivot about shafts 131and 132, respectively (FIGS. 16 and 17).

FIGS. 18A, 18B, and 18C further illustrate three general operativepositions of damper assembly 1150. In FIG. 18A, damper assembly 1150 isin a third closed operative position which prevents ambient air fromflowing into and through duct D50 and past damper assembly 1150. In FIG.18B, damper assembly 1150 is rotated from the third closed operativeposition of FIG. 18A in the direction of arrow B (FIG. 18A) to thesecond open operative position allowing ambient air to follow the pathindicated by arrow A20 in FIG. 18B and FIG. 17. In FIG. 18C, damperassembly 1150 is rotated from the third closed operative position ofFIG. 18A in the direction of arrow A (FIG. 18A) to the first openoperative position allowing ambient air to follow the path indicated byarrow A10 in FIG. 18C and FIG. 16. As would be appreciated by those ofskill in the art, damper assembly 1150 can be rotated (1) from thesecond open operative position through the third closed operativeposition to the first open operative position, and vice versa, (2) fromthe second open operative position back to the third closed operativeposition, and (3) from the first open operative position back to thethird closed operative position. The majority of the time, damperassembly 1150 will be in either the first or second open operativeposition.

The particular location of damper assembly 1150 when it is in the first(or second) open operative position is determined by the algorithmearlier described herein. The algorithm determines at any given instantin time a desired flow rate of air, either into the heat exchange unit120 via the airflow path generally located by arrow A10 or bypassingheat exchange unit 120 via the air flow path generally located by arrowA20. As is indicated in FIG. 21, once controller 300 (FIG. 21)determines that damper assembly 1150 needs to be operated in, forexample, the second operative position of FIG. 18B, controller 300 isusing the previously described algorithm (or another desired algorithm)to continuously calculate a desired flow rate of air, and send signalsto motor 86 to adjust the position of damper assembly 1150 to increaseor decrease the flow rate of air along the path generally indicated byarrow A20 (FIG. 17). Motor 86 turns shaft 131A, and therefore damperassembly 1150 and shaft 131, in the direction of arrow B to move damperassembly 1150 from the third operative position of FIG. 18A to thesecond operative position of FIG. 18B. Minute adjustments (i.e., minuterotation) of the damper drum 138 in damper assembly 1150 continues tooccur to meet the algorithm calculated air flow rate requirements.

FIG. 19 is a perspective view illustrating construction details ofdamper assembly 1150 and its operatively associated divider panel 135.When ambient air is traveling along the path indicated by arrow A20,panel 135 (along with associated circumscribing walls of duct D50)prevents ambient air from crossing over into the path that is followedby air traveling along a path indicated by arrow A10. When ambient airis traveling along the path indicated by arrow A10, panel 135 (alongwith the associated circumscribing walls of duct D50) prevents ambientair from crossing over into the path that is followed by air travelingas indicated by arrow A20.

Damper assembly 1150 includes scalloped edges 139 (FIG. 19) and 163(FIG. 23). The shape and dimension of edge 139 is presently equivalentto that of edge 163, although that need not be the case. Damper 1150also includes a top generally semicircular panel 136 and a bottomgenerally semicircular panel 137. The shape and dimension of panel 136is presently equivalent to that of panel 137, although that need not bethe case. Semicircular wall 138 extends between and interconnects spacedapart, parallel panels 136 and 137. As is illustrated in FIG. 23,contoured panel 64 extends between scalloped edges 139 and 163. Damperassembly 1150 can be formed in any desired manner and can comprise asolid piece of material. It is presently preferred that damper assembly1150 be hollow in order to reduce the amount of material required toproduce a system in accordance with the invention.

The damper assembly 1150A in FIG. 20 is comparable to damper assembly1105, provided, however, that damper assembly 1150A is truncated toproduce flat surface 65. If desired, damper assembly 1150A can betruncated to form, instead of flat truncated surface 65, the arcuateconcave surface indicated by dashed line 66. Scalloped edge 139 includessemi-elliptical concave portions 140 and 141, semi-elliptical convexportion 142, and quarter-elliptical convex portions 143 and 144. Theshape and dimension of a scalloped edge 139, 163 can vary as desired. Byway of example, and not limitation, concave portions 140 and 141 can besemi-circular and not semi-elliptical.

Any desired system can be devised to seal appropriately the periphery ofdamper assembly 1150 to prevent air from flowing around damper assembly1150 unless damper assembly 1150 is in the first or second openoperative position. In FIG. 21, for example, elongate fixed foam or feltor rubber strips or gaskets 84 and 85 sealingly engage the top 136 andbottom of damper assembly 1150, and elongate fixed foam or felt orrubber strips sealingly engage portions of cylindrical outer surface138. In FIG. 21, damper assembly 1150 is in the third closed operativeposition. In the third operative position, the entire length of eachscalloped edge 139, 163 is spaced apart and forwardly from strips 82,83, 84, 85 so that air cannot enter duct D50 and flow past damperassembly 1150. Consequently, edges 139 and 163 are not visible in FIG.21 because they are on the other side of and spaced apart from strips82, 83, 84, 85 as shown in FIG. 24. Seal 82 is fixedly attached to wall80. Seal 83 is fixedly attached to wall 81. Seal 84 is fixedly securedto the top of duct D50. Seal 85 is fixedly attached to the bottom ofduct D50. In FIG. 24, the location of strip 84 is indicated by dashedline 84A. Bushings 169 and 168 sealingly engage shafts 131 and 131A,respectively. Outer surface 138 (FIG. 19) of damper assembly 1150sealingly slides over strips 82 and 83. Top 136 of damper assembly 1150sealingly slides over strip 84. Bottom 137 of damper assembly 1150sealingly slides over strip 85.

FIG. 22 depicts how a rotatable shaft 131B can extend completely throughand be fixedly attached to a damper assembly 1150.

In FIG. 24, dashed lines 90 and 91 indicate reinforcing interior panels,or ribs, that extend from the top 136 to the bottom 137 of damperassembly 1150. The ribs 90 and 91 are spaced about one-half inch behindthe concave portions 140 and 141 (FIG. 10) of the scalloped edges 139and 163 of damper assembly 1150.

As can be seen in FIGS. 18A and 19, the upper edges 133 and 134 ofdamper assembly 1150 are not collinear, but instead together form aninner obtuse angle of less than one hundred and eighty degrees. As aresult, damper assembly 1150 is larger than one-half of a cylinder. Thisprovides space for scalloped edges 139 and 163 such that in FIG. 24,edges 139 and 163 are in their entirety on the same side of wall 81 andseal 84 as is divider panel 135. No portion of edges 139 and 163 extendspast walls 80 and 81 toward the opening D50A of duct D50. If desired,damper assembly 1150 can, as indicated by dashed line 67 in FIG. 20, beformed such that edges 133 and 134 are collinear. In that case, seals82, 83, 84, 85 may have to be repositioned to insure that when damperassembly 1150 is in the third operative position illustrated in FIG. 24,no portion of edges 139 and 163 extends past seals 82 to 85 towardopening D50A.

The diameter, indicated by arrows F in FIG. 23, of damper assembly 1150is presently ten inches, and the height, indicated by arrows G in FIG.23, of damper assembly 1150 is presently sixteen inches. In the majorityof cases, the diameter of damper assembly 1150 will be in the range ofnine to eleven inches, and the height of damper assembly 1150 will be inthe range of fifteen to seventeen inches. The diameter of damperassembly 1150 may, however, be in the range of six to twelve inches andthe height of damper may be in the range of sixteen to thirty inches.The diameter and height of damper assembly 1150 are varied to meetdesired air flow requirements, to meet sizing requirements of ductingand air conditioning units, and/or to meet other design criteria.

When damper assembly 1150 is in the economizer mode illustrated in FIG.18B, the position of damper assembly 1150 is, for a damper assembly 1150with a diameter of ten inches and a height of sixteen inches, adjustedto vary the air flow A20 between 100 cfm (cubic feet per minute) and 700cfm. When the damper assembly 1150 is in the heat recovery modeillustrated in FIG. 18C, the position of damper assembly 1150 is, for adamper assembly 1150 with a diameter of ten inches and a height ofsixteen inches, adjusted to vary the air flow A10 between 100 cfm and450 cfm. One way to increase the airflow A10 or A20 for a given amountof revolution of damper assembly 1150 is to make the damper assembly1150 taller. Another way to increase the airflow A10 or A20 for a givenamount of revolution of damper assembly 1150 is to increase the damperassembly diameter. Still another way to increase the airflow A10 or A20for a given amount of revolution of damper assembly 1150 is to reducethe height of damper assembly 1150 and increase the diameter of thedamper assembly 1150 by a desired amount. Yet another way to increasethe airflow of damper assembly 1150 is to increase the height anddiameter of damper assembly 1150. Reducing the airflow of damperassembly 1150 is accomplished by carrying out the reverse of theforegoing size increasing procedures. The minimal desired airflow A10 orA20 into a classroom is typically 100 cfm.

The airflow A20 in the economizer mode of FIG. 18B is increased byrotating damper assembly 1150 and shafts 131 and 131A in the directionof arrow B (FIG. 18A). The incorporation in damper assembly 1150 ofscalloped edge 139 is important in this respect because with each degreeof rotation of damper assembly 1150 in the direction of arrow B, theamount of increase in airflow A20 is less than if edge 139 were straightand parallel to the centerline of damper assembly 1150. The centerlineof damper assembly 1150 extends through the center of shafts 131 and131A. As damper assembly 1150 begins to open to permit airflow A20, suchairflow A20 initially can pass only through the “valleys” 140 and 141(FIG. 20) of edge 39. This facilitates being able to adjust the airflowin small increments. In the practice of the invention, it is importantto be able to adjust the airflow by increments at least as small as oneto two percent of the maximum airflow in the heat recovery mode and theeconomizer mode. Consequently, for example, if the maximum airflow inthe economizer mode is 700 cfm, it is important to be able to adjust theair flow by 7 to 14 cfm. Scalloped edge 139 facilitates such airflowadjustments.

The airflow A10 in the heat recovery mode is increased by rotatingdamper assembly 1150 and shafts 131 and 131A in the direction of arrow A(FIG. 18A). The incorporation in damper assembly 1150 of scalloped edge163 is important in this respect because with each degree of rotation ofdamper assembly 1150 in the direction of arrow A, the amount of increasein airflow A10 is less than if edge 139 were straight and parallel tothe centerline of damper assembly 1150. The centerline of damperassembly 1150 extends through the center of shafts 131 and 131A. Asdamper assembly 1150 begins to open to permit airflow A10, such airflowA10 initially can pass only through the “valleys” of edge 163. Thisfacilitates being able to adjust the airflow in small increments. In thepractice of the invention, it is important to be able to adjust the byincrements at least as small as one to two percent of the maximumairflow in the heat recovery mode and the economizer mode. Consequently,for example, if the maximum airflow A10 in the heat recovery mode is 450cfm, it is important to be able to adjust the air flow by four and onehalf cfm to nine cfm. Scalloped edge 163 facilitates such airflowadjustments.

The shape and dimension of scalloped edges 139 and 163 can vary asdesired. The presently preferred design of edges 139 and 163 utilizesvalleys 140 and 141, and peaks 142 which each correspond to one-half(valleys 140 and 141, and peak 142) or one-quarter (peaks 143 and 144)of the shape of an ellipse. The number and shape of such peaks andvalleys can vary as desired. For example, valleys 140 and 141 may have acircular contour; or, edge 139 can have a saw tooth configuration. Oneor more openings, such as the opening depicted by dashed line 192 inFIG. 20, can be formed though damper assembly 1150 near an edge 139,163.

In one embodiment of the invention the diameter and/or height of damperassembly 1150 is decreased sufficiently such that the air flow in theeconomizer mode is 70 to 450 cfm; and, the air flow in the heat recoverymode is 70 to 300 cfm.

In another embodiment of the invention, the diameter and/or height ofdamper assembly 1150 is increased sufficiently such that the air flowA20 in the economizer mode is 150 to 2100 cfm; and, the air flow A10 inthe energy recovery mode is in the range of 70 to 1400 cfm.

Although the diameter and height of damper assembly 1150 can vary asdesired, the diameter of damper assembly 1150 typically presentlycorresponds to the width of the plenum D40 of air conditioning unit 220;and, the height of damper assembly 1150 presently typically generallycorresponds to the height of the heat exchange unit 120. The diameter ofdamper assembly 1150 can be based on the available scalloped open airspaces. A larger diameter provides more air flow. A smaller diameterprovides less air flow.

Accordingly, in general, during the practice of the invention, theairflow A20 in the economizer mode can be in the range of 70 to 2100cfm, and the airflow A10 in the heat recovery mode can be in the rangeof 70 to 1400 cfm.

The maximum possible airflow during the economizer mode is always begreater than the maximum possible airflow during the heat recovery mode.

In FIG. 21, motor 86 is utilized to rotate shaft 131A, and thereforedamper assembly 1150, in the direction of arrow A and in a directionopposite that of arrow A. Motor 86 can be a stepper motor or aninfinitely modulating motor. Motor 86 preferably is able to rotatedamper assembly 1150 in increments at least as small as 0.1 degree.

A particular advantage of the damper assembly 1150 is that it enablessmall incremental changes in air flow while at the same time enablingand controlling the modulation of two separate airflows A10 and A20.Airflow A10 is modulated independently of airflow A20. If airflow A10 isbeing utilized during operation of the system of the invention, airflowA20 is not being utilized, and vice versa.

One goal of the invention is to make the increase in airflow A10 or A20linear with respect to the amount of rotation of damper assembly 1150.As damper assembly 1150 is rotated to permit airflow A10 or A20 toincrease, the cross-sectional area through which airflow A10 or A20moves increases along with the perimeter of the cross sectional area.Preferably, the cross sectional area should change proportionally to theperimeter of the cross sectional area to permit linear, or substantiallylinear, control of the volume of air passing through the cross sectionalarea. Ideally, a given increase in the cross-sectional area produces alike increase in the perimeter of the cross-sectional area, e.g., a 10%increase in cross-sectional area produces a 10% increase in theperimeter of the cross-sectional area.

In the presently preferred embodiment of the invention, damper assembly1150 is rotated a maximum of 75 degrees from the third operativeposition of FIG. 18A in the direction of arrow A; and, similarly isrotated a maximum of 75 degrees from the third operative position ofFIG. 18A in the direction of arrow B. Such maximum rotation values canbe adjusted as desired.

In FIG. 18B, the cross-sectional area through which airflow A20 moves isbounded by seal 83, edge 139 of damper assembly 1150, seal 85, and seal84 (FIG. 21). In FIG. 18C, the cross-sectional area through whichairflow A10 moves is bounded by seal 82, edge 63, seal 85, and seal 84.When damper assembly 1150 is rotated to increase the flow of air throughone of these cross-sectional areas, the pressure drop produced by theair as it moves through the cross-sectional areas decreases. If there isa pressure drop reduction produced when air flow A10 moves past damperassembly 1150, then there is a corresponding increase in the pressuredrop produced as the air passes through heat exchange unit 120.

In addition to being utilized in connection with air conditioning(heating/cooling) systems, damper assembly 1150 can be utilized in anyatmospheric pressure gas/vapor regulating system which requires thedivision and modulation of a single gas/vapor stream into two separateindependent gas/vapor streams.

While damper assembly 1150 and other system components can be fabricatedfrom any desired material, it is presently preferred that damperassembly 1150 be constructed from a medium to high strength materialsuch as, for example, carbon steel, polymer or other materials. Theparticular material selected will depend on system pressures,corrosivity of the gas/vapor, and the maximum allowable smoke spread andflame development requirements of NFPA and local building codes. Thepreferred maximum leakage for seals 82 to 85 (FIG. 21) in an airconditioning system when damper assembly 1150 is in the third operativeposition is 2% of the design air flow at a system pressure of threeinches water column pressure.

Motor 86, or any other desired actuator system, is preferably a lowvoltage (less than 115 volts) or line voltage (115 volts to 600 volts)motor capable of rotating shaft 131A through a minimum of 180 degrees ofrotation, and includes a position feedback that can recognize whendamper assembly 1150 is in the third operative position (shut offposition) of FIG. 18A and can recognize any other desired position ofdamper assembly 1150. Alternate position sensing systems can beutilized, such as a magnetic end switch device attached to damperassembly 1150 and a portion of duct D50 that circumscribes and housesdamper assembly 1150.

Having described my invention in such terms as to enable those skilledin the art to make and use the invention, and having described the bestmode thereof, I claim:
 1. In combination with a building structureincluding a room with a maximum occupancy rating of at least twentypeople per 1,000 sq. ft of occupied space, an air conditioning systemincluding a heat transfer coil, a first section of duct (D40) leading tothe heat transfer coil to direct supply air from the building structureover the coil, and a second section of duct (D20) leading away from theheat transfer coil to carry air from the coil back into the building,the improvements in the building structure comprising (a) a ventilationcontrol unit attached to the first section of duct and including (i) ahousing (230), (ii) a heat exchange unit (120), (iii) a third section ofduct (D10) connected to said first section of duct (D40) to direct afirst portion of return air from the room into said first section ofduct, (iv) a fourth section of duct (D30) to direct a second portion ofreturn air from the room over said heat exchange unit, (v) a fifthsection of duct (D50) to direct ambient air over said heat exchange unitinto said third section of duct (D10), said heat exchange unitmaintaining said second portion of return air separate from said ambientair and transferring heat between said second portion of return air andsaid ambient air, and directly to said third section of duct (D10) bybypassing said heat exchange unit, (vi) a sixth section of duct (D60) todirect said second portion of return air from said heat exchange unitinto the outside atmosphere, (vii) an outlet damper assembly (160)controlling the flow of said second portion of return air over said heatexchange unit (120) and into the outside atmosphere, (viii) a generallysemi-cylindrical inlet damper assembly controlling the flow of saidambient air into said ventilation control unit and including a member(38, 1150) rotatable between at least three operative positions, a firstoperative position directing ambient air only over said heat exchangeunit (120), a second operative position bypassing said heat exchangeunit and directing ambient air only directly to said third section ofduct (D10) to combine with said first portion of return air, and a thirdoperative position preventing said ambient air from flowing to said heatexchange unit and to said third section of duct (D10) to combine withsaid first portion of return air, (ix) a control unit operativelyassociated with said inlet and outlet damper assemblies to control therate of flow of said ambient air and said second portion of said returnair, respectively, through said inlet and outlet damper assemblies, (x)a first flow sensor operatively associated with said inlet damperassembly to generate signals to said control unit representing the rateof flow of ambient air through said inlet damper assembly, (ix) a secondflow sensor operatively associated with said outlet damper assembly togenerate signals to said control unit representing the rate of flow ofsaid second return air portion through said outlet damper assembly, (x)a CO2 sensor in the room to generate signals to said control unitrepresenting the concentration of CO2 in the air in the room; (b) afirst fan to direct said ambient air into said fifth section of duct,over said heat exchanger, and into said first section of duct; (c) asecond fan to direct said second portion of return air from said fourthsection of duct, and through said fourth section of duct over said heatexchanger, and into the atmosphere; (d) a control algorithm in saidcontrol unit to calculate, at stepped spaced apart increasing roomventilation rates, increasing CO2 concentrations in the air in the roomthat are below a maximum desired CO2 concentration in the room.